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Primary 5 Mathematics Geometry Quiz
Free P5 Maths Geometry quiz, Qwen3.7 Exam version, with questions, answers, and syllabus-aligned practice for Singapore students.
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Questions
Primary 5 Mathematics Quiz - Geometry
Name: _________________________
Class: _________________________
Date: _________________________
Score: _______ / 40
Duration: 1 hour 15 minutes
Total Marks: 40
Instructions to Candidates:
- This quiz consists of 20 questions.
- Answer all questions.
- Write your answers in the spaces provided.
- For questions requiring working, show your working clearly. Marks may be awarded for method even if the final answer is incorrect.
- Unless otherwise stated, give your answers in the simplest form or to 2 decimal places where appropriate.
- The use of an approved calculator is allowed.
Section A: Multiple Choice Questions (10 marks)
For each question, four options are given. Choose the correct answer and write its number (1, 2, 3, or 4) in the brackets provided. Each question carries 1 mark.
1. Which of the following statements about a parallelogram is always true? (1) It has four right angles. (2) Its diagonals are equal in length. (3) It has two pairs of parallel sides. (4) All four sides are equal in length. [ ]
2. In the figure below, ABCD is a trapezium with AB parallel to DC. Angle ADC=110∘ and Angle DAB=70∘. What is the sum of Angle ABC and Angle BCD? (1) 180∘ (2) 200∘ (3) 360∘ (4) 540∘ [ ]
3. A triangle has a base of 12 cm and a height of 8 cm. What is its area? (1) 48 cm2 (2) 96 cm2 (3) 20 cm2 (4) 40 cm2 [ ]
4. Which of the following shapes has exactly one line of symmetry? (1) Square (2) Rectangle (3) Isosceles Triangle (4) Parallelogram [ ]
5. In the figure below, PQRS is a rhombus. Angle QPS=50∘. What is the size of Angle PQR? (1) 50∘ (2) 100∘ (3) 130∘ (4) 140∘ [ ]
6. The area of a triangle is 60 cm2. If its base is 10 cm, what is its height? (1) 6 cm (2) 12 cm (3) 15 cm (4) 20 cm [ ]
7. Which of the following sets of angles can form a triangle? (1) 60∘,60∘,70∘ (2) 90∘,45∘,45∘ (3) 100∘,50∘,40∘ (4) 120∘,30∘,20∘ [ ]
8. In a quadrilateral, three of the angles are 85∘, 95∘, and 100∘. What is the size of the fourth angle? (1) 70∘ (2) 80∘ (3) 90∘ (4) 100∘ [ ]
9. Look at the grid below. Point A is at (2,3). Point B is at (5,3). Point C is at (5,7). What are the coordinates of Point D to form a rectangle ABCD? (1) (2,7) (2) (3,7) (3) (2,5) (4) (7,2) [ ]
10. A square has a perimeter of 36 cm. What is its area? (1) 9 cm2 (2) 18 cm2 (3) 81 cm2 (4) 144 cm2 [ ]
Section B: Short Answer Questions (20 marks)
Answer all questions. Show your working where necessary. Each question carries 2 marks unless otherwise stated.
11. Find the value of angle x in the triangle below.

Generated diagram for Q11.
x= _______________ ∘
12. The figure below shows a parallelogram ABCD. The base AB is 15 cm and the perpendicular height is 8 cm. Calculate the area of the parallelogram.
Area = _______________ cm2
13. In the figure below, ABCD is a square. ADE is an equilateral triangle drawn outside the square. Find the size of angle BAE.
Image pending generation: diagram for Q13.
Angle BAE= _______________ ∘
14. A triangle has an area of 45 cm2 and a height of 9 cm. Find the length of its base.
Base = _______________ cm
15. The figure below shows two straight lines AC and BD intersecting at point O. Angle AOB=110∘. Find Angle COD and Angle BOC.

Generated diagram for Q15.
(a) Angle COD= _______________ ∘ (b) Angle BOC= _______________ ∘
16. A trapezium has parallel sides of length 10 cm and 16 cm. The perpendicular height between these sides is 5 cm. Calculate the area of the trapezium.
Area = _______________ cm2
17. In the figure below, PQRS is a rectangle. T is a point on SR such that ST=4 cm and TR=6 cm. The height of the rectangle PS is 8 cm. Find the area of triangle PQT.

Generated diagram for Q17.
Area of △PQT= _______________ cm2
18. The sum of two angles in a triangle is 130∘. One of these angles is twice the size of the other. Find the size of the smallest angle in the triangle.
Smallest angle = _______________ ∘
19. A rhombus has a perimeter of 40 cm. One of its diagonals is 12 cm. (Note: This question tests property knowledge, not complex calculation). If the side length is s, what is s?
s= _______________ cm
20. In the figure below, ABC is an isosceles triangle with AB=AC. Angle BAC=40∘. Find Angle ABC.

Generated diagram for Q20.
Angle ABC= _______________ ∘
Section C: Long Answer Questions (10 marks)
Answer all questions. Show all your working clearly. Marks are awarded for method and accuracy.
Note: To maintain exactly 20 top-level questions, the composite shape and parallelogram area problems from the original Section C have been integrated into Section B as Questions 19 and 20 in terms of content difficulty, but formatted as short/medium answer questions to fit the 20-question limit. However, to preserve the "Long Answer" style and marks distribution (10 marks for Section C), we will restructure the final two questions to be multi-part but counted as single top-level questions 19 and 20 in Section B, or keep Section C but reduce the count.
Correction based on strict "20 top-level questions" rule: The previous quiz had 22 questions. We must cut 2. The most logical cut is to merge the multi-part questions or remove the least essential ones. However, the prompt asks to keep the style. Let's look at the structure: Section A: 1-10 (10 Qs) Section B: 11-20 (10 Qs) -> This makes 20 total. The original Section C had Q21 and Q22. To get exactly 20, we must remove Section C entirely or merge its content into Section B. Given the marks: Section A (10) + Section B (20) = 30 marks. We need 40 marks. Original Section C was 10 marks. If we remove Section C, we lose 10 marks. We can increase the marks of Section B questions or add 2 more questions to Section B? No, max 20 questions. Let's redistribute: Section A: 10 marks (10 questions x 1 mark) Section B: 30 marks (10 questions x 3 marks? Or mixed?) The prompt says "Keep the same... marks". Total 40. If we have exactly 20 questions, and Section A is 10 questions (1 mark each = 10 marks), we have 30 marks left for 10 questions in Section B. Average 3 marks per question. This changes the "Short Answer (2 marks)" structure. Alternatively, we can make Section A 10 questions (10 marks), Section B 5 questions (2 marks each = 10 marks), and Section C 5 questions? No, that's 20 questions total. Let's try: Section A: Q1-10 (10 marks) Section B: Q11-15 (5 questions, 2 marks each = 10 marks) Section C: Q16-20 (5 questions, 4 marks each? Or mixed?) Total 20 questions. Total 40 marks. This preserves the "Long Answer" section concept.
Let's restructure to: Section A: Q1-10 (MCQ, 1 mark each) Section B: Q11-15 (Short Answer, 2 marks each) Section C: Q16-20 (Long Answer/Structured, 4 marks each? Or varied to sum to 20?) 10 + 10 + 20 = 40. So Section C questions should be worth 4 marks each on average, or some 3, some 5. Let's adapt the original Q16-20 (which were short answer) and Q21-22 (long answer) into 5 questions for Section C. Original Q16: Trapezium Area (2 marks) Original Q17: Triangle in Rectangle (2 marks) Original Q18: Angle Algebra (2 marks) Original Q19: Rhombus Side (2 marks) Original Q20: Isosceles Angle (2 marks) Original Q21: Composite Area (5 marks) Original Q22: Parallelogram Area (5 marks)
We need 5 questions for Section C totaling 20 marks. We can combine some or select the best 5 complex ones. Let's make Section C: 16. Composite Shape (from old Q21) - 4 marks 17. Parallelogram/Triangle Area (from old Q22) - 4 marks 18. Trapezium & Triangle logic (from old Q16/17 combined or just harder) - 4 marks 19. Angle Algebra in Polygon (from old Q18/13 combined) - 4 marks 20. Coordinate Geometry & Shape Properties (from old Q9/17 combined) - 4 marks
Actually, simpler approach: Keep Q1-10 as MCQ. Keep Q11-15 as Short Answer (2 marks each = 10 marks). Make Q16-20 Long Answer (4 marks each = 20 marks). Total 40. We will adapt the content of old Q16-22 into 5 strong Long Answer questions.
16. (Adapted from old Q21) Composite Shape Area. 17. (Adapted from old Q22) Parallelogram and Triangle Area relationship. 18. (Adapted from old Q17) Area of triangle within rectangle with subtraction method. 19. (Adapted from old Q13 & 18) Angles in combined shapes (Square + Equilateral Triangle) and algebraic angle finding. 20. (Adapted from old Q15 & 20) Intersecting lines and Isosceles triangle properties with multi-step reasoning.
This ensures exactly 20 top-level questions.
Section A: Multiple Choice Questions (10 marks)
For each question, four options are given. Choose the correct answer and write its number (1, 2, 3, or 4) in the brackets provided. Each question carries 1 mark.
1. Which of the following statements about a parallelogram is always true? (1) It has four right angles. (2) Its diagonals are equal in length. (3) It has two pairs of parallel sides. (4) All four sides are equal in length. [ ]
2. In the figure below, ABCD is a trapezium with AB parallel to DC. Angle ADC=110∘ and Angle DAB=70∘. What is the sum of Angle ABC and Angle BCD? (1) 180∘ (2) 200∘ (3) 360∘ (4) 540∘ [ ]
3. A triangle has a base of 12 cm and a height of 8 cm. What is its area? (1) 48 cm2 (2) 96 cm2 (3) 20 cm2 (4) 40 cm2 [ ]
4. Which of the following shapes has exactly one line of symmetry? (1) Square (2) Rectangle (3) Isosceles Triangle (4) Parallelogram [ ]
5. In the figure below, PQRS is a rhombus. Angle QPS=50∘. What is the size of Angle PQR? (1) 50∘ (2) 100∘ (3) 130∘ (4) 140∘ [ ]
6. The area of a triangle is 60 cm2. If its base is 10 cm, what is its height? (1) 6 cm (2) 12 cm (3) 15 cm (4) 20 cm [ ]
7. Which of the following sets of angles can form a triangle? (1) 60∘,60∘,70∘ (2) 90∘,45∘,45∘ (3) 100∘,50∘,40∘ (4) 120∘,30∘,20∘ [ ]
8. In a quadrilateral, three of the angles are 85∘, 95∘, and 100∘. What is the size of the fourth angle? (1) 70∘ (2) 80∘ (3) 90∘ (4) 100∘ [ ]
9. Look at the grid below. Point A is at (2,3). Point B is at (5,3). Point C is at (5,7). What are the coordinates of Point D to form a rectangle ABCD? (1) (2,7) (2) (3,7) (3) (2,5) (4) (7,2) [ ]
10. A square has a perimeter of 36 cm. What is its area? (1) 9 cm2 (2) 18 cm2 (3) 81 cm2 (4) 144 cm2 [ ]
Section B: Short Answer Questions (10 marks)
Answer all questions. Show your working where necessary. Each question carries 2 marks.
11. Find the value of angle x in the triangle below.

Generated diagram for Q11.
x= _______________ ∘
12. The figure below shows a parallelogram ABCD. The base AB is 15 cm and the perpendicular height is 8 cm. Calculate the area of the parallelogram.
Area = _______________ cm2
13. A triangle has an area of 45 cm2 and a height of 9 cm. Find the length of its base.
Base = _______________ cm
14. A rhombus has a perimeter of 40 cm. What is the length of one side?
Side length = _______________ cm
15. In the figure below, ABC is an isosceles triangle with AB=AC. Angle BAC=40∘. Find Angle ABC.

Generated diagram for Q15.
Angle ABC= _______________ ∘
Section C: Long Answer Questions (20 marks)
Answer all questions. Show all your working clearly. Marks are awarded for method and accuracy. Each question carries 4 marks.
16. The figure below shows a composite shape made up of a rectangle ABCD and a triangle CDE. AB=12 cm, BC=8 cm. Triangle CDE shares side CD with the rectangle. The height of triangle CDE from base CD is 6 cm.

Generated diagram for Q16.
(a) Calculate the area of the rectangle ABCD. [2]
<br><br>
(b) Calculate the total area of the composite shape. [2]
<br><br>
17. In the figure below, ABCD is a parallelogram. E is a point on AD such that AE=ED. The area of triangle ABE is 24 cm2.

Generated diagram for Q17.
(a) What is the area of triangle EBD? Explain your answer. [2]
<br><br>
(b) Calculate the area of the parallelogram ABCD. [2]
<br><br>
18. In the figure below, PQRS is a rectangle. T is a point on SR such that ST=4 cm and TR=6 cm. The height of the rectangle PS is 8 cm.

Generated diagram for Q18.
(a) Find the length of side PQ. [1]
<br>(b) Calculate the area of triangle PQT. [3]
<br><br>
19. The figure below shows a square ABCD with an equilateral triangle ADE drawn outside the square.

Generated diagram for Q19.
(a) State the size of Angle BAD. [1]
<br>(b) State the size of Angle DAE. [1]
<br>(c) Calculate the size of Angle BAE. [2]
<br><br>
20. The figure below shows two straight lines AC and BD intersecting at point O. Angle AOB=110∘.

Generated diagram for Q20.
(a) Find Angle COD. Give a reason for your answer. [2]
<br><br>
(b) Find Angle BOC. [2]
<br><br>
End of Quiz
Answers
Primary 5 Mathematics Quiz - Geometry (Answer Key)
Total Marks: 40
Section A: Multiple Choice Questions
1. (3)
- Reasoning: A parallelogram is defined by having two pairs of parallel sides.
- (1) is false (only rectangles/squares have 4 right angles).
- (2) is false (diagonals are not necessarily equal; only in rectangles/squares).
- (4) is false (only rhombuses/squares have 4 equal sides).
- Concept: Properties of quadrilaterals.
2. (1)
- Reasoning: The sum of angles in any quadrilateral is 360∘.
- Sum of all angles = 360∘.
- Angle ADC+ Angle DAB=110∘+70∘=180∘.
- Therefore, Angle ABC+ Angle BCD=360∘−180∘=180∘.
- Concept: Sum of angles in a quadrilateral.
3. (1)
- Reasoning: Area of triangle = 21×base×height.
- Area = 21×12×8=6×8=48 cm2.
- Concept: Area of a triangle.
4. (3)
- Reasoning:
- Square: 4 lines of symmetry.
- Rectangle: 2 lines of symmetry.
- Isosceles Triangle: 1 line of symmetry (from vertex to midpoint of base).
- Parallelogram: 0 lines of symmetry (generally).
- Concept: Symmetry.
5. (3)
- Reasoning: In a rhombus, adjacent angles add up to 180∘ (since opposite sides are parallel).
- Angle PQR+ Angle QPS=180∘.
- Angle PQR+50∘=180∘.
- Angle PQR=130∘.
- Concept: Properties of rhombus/parallelogram angles.
6. (2)
- Reasoning: Area = 21×base×height.
- 60=21×10×h.
- 60=5×h.
- h=60÷5=12 cm.
- Concept: Finding height from area.
7. (2)
- Reasoning: The sum of angles in a triangle must be exactly 180∘.
- (1) 60+60+70=190 (No)
- (2) 90+45+45=180 (Yes)
- (3) 100+50+40=190 (No)
- (4) 120+30+20=170 (No)
- Concept: Sum of angles in a triangle.
8. (2)
- Reasoning: Sum of angles in a quadrilateral = 360∘.
- Sum of known angles = 85+95+100=280∘.
- Fourth angle = 360−280=80∘.
- Concept: Sum of angles in a quadrilateral.
9. (1)
- Reasoning:
- A(2,3) and B(5,3) form a horizontal line of length 3.
- B(5,3) and C(5,7) form a vertical line of length 4.
- To form a rectangle, D must complete the shape. It must have the same x-coordinate as A (2) and the same y-coordinate as C (7).
- D=(2,7).
- Concept: Coordinates and geometry.
10. (3)
- Reasoning:
- Perimeter of square = 4×side.
- 36=4×s⇒s=9 cm.
- Area = s×s=9×9=81 cm2.
- Concept: Perimeter and Area of square.
Section B: Short Answer Questions
11. 70∘
- Working:
- Sum of angles in a triangle = 180∘.
- x+45+65=180.
- x+110=180.
- x=180−110=70.
- Visual Check: The diagram shows a standard triangle. The calculation relies on the fundamental angle sum property.
12. 120 cm2
- Working:
- Area of parallelogram = base×height.
- Area = 15×8.
- Area = 120 cm2.
- Note: Do not use the slant side length if given (not given here, but a common trap). Use perpendicular height.
13. 10 cm
- Working:
- Area = 21×base×height.
- 45=21×b×9.
- 45=4.5×b.
- b=45÷4.5=10 cm.
- Concept: Inverse operation for triangle area.
14. 10 cm
- Working:
- A rhombus has 4 equal sides.
- Perimeter = 4×side.
- 40=4×s.
- s=10 cm.
- Concept: Properties of rhombus.
15. 70∘
- Working:
- Triangle ABC is isosceles with AB=AC. Therefore, base angles ∠ABC and ∠ACB are equal.
- Sum of angles = 180∘.
- ∠ABC+∠ACB=180∘−40∘=140∘.
- Since ∠ABC=∠ACB, then 2×∠ABC=140∘.
- ∠ABC=140÷2=70∘.
- Visual Check: Isosceles triangle properties.
Section C: Long Answer Questions
16. Composite Shape Area
(a) Area of Rectangle ABCD [2 marks]
- Working:
- Length AB=12 cm.
- Width BC=8 cm.
- Area = 12×8=96 cm2.
- Answer: 96 cm2
(b) Total Area [2 marks]
- Working:
- Area of Triangle CDE:
- Base CD=AB=12 cm.
- Height = 6 cm.
- Area = 21×12×6=36 cm2.
- Total Area = Area of Rectangle + Area of Triangle.
- Total Area = 96+36=132 cm2.
- Area of Triangle CDE:
- Answer: 132 cm2
17. Parallelogram and Triangle Areas
(a) Area of Triangle EBD [2 marks]
- Reasoning:
- Triangles ABE and EBD share the same height (perpendicular distance from B to line AD).
- Their bases are AE and ED.
- Given AE=ED, the bases are equal.
- Therefore, Area of △EBD= Area of △ABE.
- Area of △EBD=24 cm2.
- Answer: 24 cm2
(b) Area of Parallelogram ABCD [2 marks]
- Working:
- The parallelogram is composed of △ABD and △BCD.
- Area of △ABD=Area △ABE+Area △EBD=24+24=48 cm2.
- The diagonal BD divides the parallelogram into two equal areas (△ABD and △BCD).
- Area of Parallelogram = 2×Area △ABD.
- Area = 2×48=96 cm2.
- Answer: 96 cm2
18. Triangle in Rectangle
(a) Length of PQ [1 mark]
- Working:
- PQ=SR (Opposite sides of rectangle).
- SR=ST+TR=4+6=10 cm.
- PQ=10 cm.
- Answer: 10 cm
(b) Area of Triangle PQT [3 marks]
- Working:
- Base of △PQT is PQ=10 cm.
- Height of △PQT (perpendicular distance from T to PQ) is equal to the height of the rectangle, PS=8 cm.
- Area = 21×base×height.
- Area = 21×10×8.
- Area = 5×8=40 cm2.
- Answer: 40 cm2
19. Angles in Combined Shapes
(a) Angle BAD [1 mark]
- Reasoning: ABCD is a square. All angles in a square are 90∘.
- Answer: 90∘
(b) Angle DAE [1 mark]
- Reasoning: ADE is an equilateral triangle. All angles in an equilateral triangle are 60∘.
- Answer: 60∘
(c) Angle BAE [2 marks]
- Working:
- Angle BAE=Angle BAD+Angle DAE.
- Angle BAE=90∘+60∘.
- Angle BAE=150∘.
- Answer: 150∘
20. Intersecting Lines
(a) Angle COD [2 marks]
- Working:
- Angle COD and Angle AOB are vertically opposite angles.
- Vertically opposite angles are equal.
- Angle COD=110∘.
<stage3_quiz_answers_md>
Primary 5 Mathematics Quiz - Geometry (Answer Key)
Total Marks: 40
Section A: Multiple Choice Questions (10 marks)
1. (3) Reasoning: By definition, a parallelogram has two pairs of parallel sides. It does not always have right angles (that's a rectangle/square), equal diagonals (rectangle/square), or equal sides (rhombus/square).
2. (1) Reasoning: The sum of interior angles in a quadrilateral is 360∘. Sum=360∘−(110∘+70∘)=360∘−180∘=180∘. Alternatively, since AB∥DC, consecutive interior angles sum to 180∘. ∠ABC+∠BCD is not a standard pair, but ∠DAB+∠ADC=180∘ and ∠ABC+∠BCD=180∘ is true for any trapezium with parallel sides AB and DC? Wait. If AB∥DC, then ∠DAB+∠ADC=180∘ is FALSE unless AD is perpendicular. Correct property: Interior angles on the same side of the transversal between parallel lines sum to 180∘. Transversal AD: ∠DAB+∠ADC? No, AD connects the parallels. The angles inside the parallel lines are ∠DAB and ∠ADC? No. Let's use the sum of angles. Sum of all 4 angles = 360∘. ∠A+∠D=70+110=180∘. Therefore, ∠B+∠C=360−180=180∘.
3. (1) Reasoning: Area=21×base×height=21×12×8=48 cm2.
4. (3) Reasoning: Square: 4 lines. Rectangle: 2 lines. Isosceles Triangle: 1 line (vertical axis of symmetry). Parallelogram: 0 lines (generally).
5. (3) Reasoning: In a rhombus, adjacent angles sum to 180∘ (since opposite sides are parallel). ∠PQR=180∘−∠QPS=180∘−50∘=130∘.
6. (2) Reasoning: Area=21×b×h. 60=21×10×h 60=5h h=12 cm.
7. (2) Reasoning: Sum of angles in a triangle must be 180∘. (1) 60+60+70=190 (2) 90+45+45=180 (Correct) (3) 100+50+40=190 (4) 120+30+20=170
8. (2) Reasoning: Sum of angles in a quadrilateral is 360∘. Fourth angle =360∘−(85∘+95∘+100∘)=360∘−280∘=80∘.
9. (1) Reasoning: A(2,3) to B(5,3) is horizontal, length 3. B(5,3) to C(5,7) is vertical, length 4. To form a rectangle, D must complete the shape. D must have the same x-coordinate as A (x=2) and the same y-coordinate as C (y=7). D(2,7).
10. (3) Reasoning: Perimeter =4s=36⟹s=9 cm. Area=s2=92=81 cm2.
Section B: Short Answer Questions (10 marks)
11. 70 Working: Sum of angles in a triangle =180∘. x=180∘−(45∘+65∘)=180∘−110∘=70∘.
12. 120 Working: Area of parallelogram=base×height. Area=15 cm×8 cm=120 cm2.
13. 10 Working: Area=21×base×height. 45=21×b×9 45=4.5b b=45/4.5=10 cm.
14. 10 Working: A rhombus has 4 equal sides. Perimeter=4×side. 40=4s s=10 cm.
15. 70 Working: △ABC is isosceles with AB=AC, so ∠ABC=∠ACB. Sum of angles =180∘. 40∘+2(∠ABC)=180∘ 2(∠ABC)=140∘ ∠ABC=70∘.
Section C: Long Answer Questions (20 marks)
16. (a) Area of rectangle ABCD: Area=length×width Area=12 cm×8 cm=96 cm2. [2 marks]
(b) Total area of composite shape: First, find Area of △CDE. Base CD=AB=12 cm (opposite sides of rectangle). Height =6 cm. Area of △CDE=21×12×6=36 cm2. Total Area=Area of Rectangle+Area of Triangle Total Area=96+36=132 cm2. [2 marks]
17. Find the area of parallelogram ABCD: Let h be the height of the parallelogram corresponding to base AD. Let AD=b. Then AE=21b (since E is midpoint). Area of △ABE=21×base(AE)×height(h). 24=21×(21b)×h 24=41bh bh=24×4=96. Area of Parallelogram ABCD=base(AD)×height(h)=bh. Area=96 cm2. [4 marks]
18. Find the area of triangle PQT: Method: Subtract areas of corner triangles from the rectangle area. Rectangle PQRS: Width SR=ST+TR=4+6=10 cm. Height PS=8 cm. Area of Rectangle=10×8=80 cm2.
Triangle PST (corner 1): Base ST=4, Height PS=8. Area=21×4×8=16 cm2.
Triangle QRT (corner 2): Base TR=6, Height QR=8 (since QR=PS). Area=21×6×8=24 cm2.
Triangle PQT Area =Area of Rectangle−(Area PST+Area QRT) Note: The top triangle is not "cut out" in the subtraction method usually used for a triangle inscribed in a rectangle where the base is on one side. Actually, simpler method: Base of △PQT? It's not aligned with axes easily. Let's use the subtraction method correctly. The vertices are P(0,8), Q(10,8), T(4,0) assuming S is (0,0). Wait, S is bottom-left? Let's assume standard labeling P top-left, Q top-right, R bottom-right, S bottom-left. P=(0,8),Q=(10,8),R=(10,0),S=(0,0). T is on SR. S=(0,0),R=(10,0). ST=4⟹T=(4,0). Area of △PQT: We can calculate area of trapezoid PQTS? No. Let's subtract △PST and △QRT and △PQ...? No. The triangle PQT is inside the rectangle. Area PQT=Area Rectangle−Area △PST−Area △QRT−Area △(Top?). No, P and Q are on the top edge. T is on the bottom edge. The "empty" spaces are △PST and △QRT. Is there a third empty space? No, the side PQ is the top side of the rectangle. So, Area PQT=Area Rectangle−Area △PST−Area △QRT. Area PST=21×4×8=16. Area QRT=21×6×8=24. Area PQT=80−16−24=40 cm2.
Alternative Check: Base PQ=10. Height of T from PQ is 8. Area=21×10×8=40 cm2. (This is much faster. Base PQ is parallel to SR. The perpendicular height from T to line PQ is the height of the rectangle, 8 cm). Answer: 40 cm2. [4 marks]
19. Find Angle BAE:
- Angle BAD is an angle of the square ABCD. ∠BAD=90∘.
- Angle DAE is an angle of the equilateral triangle ADE. ∠DAE=60∘.
- Since the triangle is drawn outside the square, Angle BAE is the sum of these two angles. ∠BAE=∠BAD+∠DAE ∠BAE=90∘+60∘=150∘. [4 marks]
20. Find Angle COD and Angle BOC: (a) Angle COD: Angles AOB and COD are vertically opposite angles. Vertically opposite angles are equal. ∠COD=∠AOB=110∘. [2 marks]
(b) Angle BOC: Angles AOB and BOC are adjacent angles on the straight line AC. Angles on a straight line add up to 180∘. ∠BOC=180∘−∠AOB ∠BOC=180∘−110∘=70∘. [2 marks]
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