Secondary 4 Elementary Mathematics Quiz - Graphs Coordinate Geometry
ANSWER KEY AND MARKING SCHEME
Total Marks: 50
Section A: Basic Coordinate Geometry (Questions 1–5)
1. Gradient = 19 − 7 9 − 3 = 12 6 = 2 = \frac{19 - 7}{9 - 3} = \frac{12}{6} = 2 = 9 − 3 19 − 7 = 6 12 = 2 ✓✓
M1: Correct substitution into gradient formula
A1: Correct answer 2 2 2
Answer: 2 2 2
2. Distance = ( 4 − ( − 2 ) ) 2 + ( − 3 − 5 ) 2 = 6 2 + ( − 8 ) 2 = 36 + 64 = 100 = 10 = \sqrt{(4 - (-2))^2 + (-3 - 5)^2} = \sqrt{6^2 + (-8)^2} = \sqrt{36 + 64} = \sqrt{100} = 10 = ( 4 − ( − 2 ) ) 2 + ( − 3 − 5 ) 2 = 6 2 + ( − 8 ) 2 = 36 + 64 = 100 = 10 ✓✓
M1: Correct substitution into distance formula
A1: Correct answer 10 10 10 (accept 100 \sqrt{100} 100 )
Answer: 10 10 10 units
3. Midpoint = ( 6 + ( − 4 ) 2 , − 1 + 9 2 ) = ( 2 2 , 8 2 ) = ( 1 , 4 ) = \left(\frac{6 + (-4)}{2}, \frac{-1 + 9}{2}\right) = \left(\frac{2}{2}, \frac{8}{2}\right) = (1, 4) = ( 2 6 + ( − 4 ) , 2 − 1 + 9 ) = ( 2 2 , 2 8 ) = ( 1 , 4 ) ✓✓
M1: Correct substitution into midpoint formula
A1: Correct coordinates ( 1 , 4 ) (1, 4) ( 1 , 4 )
Answer: ( 1 , 4 ) (1, 4) ( 1 , 4 )
4. Using y − y 1 = m ( x − x 1 ) y - y_1 = m(x - x_1) y − y 1 = m ( x − x 1 ) :
y − ( − 2 ) = − 3 4 ( x − 8 ) y - (-2) = -\frac{3}{4}(x - 8) y − ( − 2 ) = − 4 3 ( x − 8 )
y + 2 = − 3 4 x + 6 y + 2 = -\frac{3}{4}x + 6 y + 2 = − 4 3 x + 6
y = − 3 4 x + 4 y = -\frac{3}{4}x + 4 y = − 4 3 x + 4 ✓✓
M1: Correct substitution into point-gradient form
A1: Correct equation y = − 3 4 x + 4 y = -\frac{3}{4}x + 4 y = − 4 3 x + 4
Answer: y = − 3 4 x + 4 y = -\frac{3}{4}x + 4 y = − 4 3 x + 4
5. Line 1: y = 3 x − 7 y = 3x - 7 y = 3 x − 7 , gradient = 3 = 3 = 3
Line 2: 6 x − 2 y + 5 = 0 ⟹ 2 y = 6 x + 5 ⟹ y = 3 x + 5 2 6x - 2y + 5 = 0 \implies 2y = 6x + 5 \implies y = 3x + \frac{5}{2} 6 x − 2 y + 5 = 0 ⟹ 2 y = 6 x + 5 ⟹ y = 3 x + 2 5 , gradient = 3 = 3 = 3 ✓
Both lines have the same gradient, therefore they are parallel. ✓
M1: Finding both gradients correctly
A1: Correct conclusion with reasoning
Answer: Yes, both have gradient 3 3 3 .
Section B: Equations of Lines and Applications (Questions 6–10)
6. Parallel to y = − 2 x + 5 y = -2x + 5 y = − 2 x + 5 , so gradient = − 2 = -2 = − 2 .
Using point A ( 1 , 4 ) A(1, 4) A ( 1 , 4 ) : y − 4 = − 2 ( x − 1 ) y - 4 = -2(x - 1) y − 4 = − 2 ( x − 1 )
y − 4 = − 2 x + 2 y - 4 = -2x + 2 y − 4 = − 2 x + 2
y = − 2 x + 6 y = -2x + 6 y = − 2 x + 6 ✓✓
M1: Identifying gradient and using point-gradient form
A1: Correct equation y = − 2 x + 6 y = -2x + 6 y = − 2 x + 6
Answer: y = − 2 x + 6 y = -2x + 6 y = − 2 x + 6
7. Gradient of given line = 1 2 = \frac{1}{2} = 2 1 .
Perpendicular gradient = − 2 = -2 = − 2 (since 1 2 × ( − 2 ) = − 1 \frac{1}{2} \times (-2) = -1 2 1 × ( − 2 ) = − 1 ). ✓
Using point B ( 3 , − 1 ) B(3, -1) B ( 3 , − 1 ) : y − ( − 1 ) = − 2 ( x − 3 ) y - (-1) = -2(x - 3) y − ( − 1 ) = − 2 ( x − 3 )
y + 1 = − 2 x + 6 y + 1 = -2x + 6 y + 1 = − 2 x + 6
y = − 2 x + 5 y = -2x + 5 y = − 2 x + 5 ✓✓
M1: Finding perpendicular gradient
M1: Correct substitution into point-gradient form
A1: Correct equation y = − 2 x + 5 y = -2x + 5 y = − 2 x + 5
Answer: y = − 2 x + 5 y = -2x + 5 y = − 2 x + 5
8. Midpoint of C D CD C D : ( − 3 + 5 2 , 2 + 10 2 ) = ( 1 , 6 ) \left(\frac{-3 + 5}{2}, \frac{2 + 10}{2}\right) = (1, 6) ( 2 − 3 + 5 , 2 2 + 10 ) = ( 1 , 6 ) ✓
Gradient of C D CD C D : 10 − 2 5 − ( − 3 ) = 8 8 = 1 \frac{10 - 2}{5 - (-3)} = \frac{8}{8} = 1 5 − ( − 3 ) 10 − 2 = 8 8 = 1
Perpendicular gradient = − 1 = -1 = − 1 ✓
Equation: y − 6 = − 1 ( x − 1 ) y - 6 = -1(x - 1) y − 6 = − 1 ( x − 1 )
y − 6 = − x + 1 y - 6 = -x + 1 y − 6 = − x + 1
y = − x + 7 y = -x + 7 y = − x + 7 ✓
M1: Finding midpoint
M1: Finding perpendicular gradient
A1: Correct equation y = − x + 7 y = -x + 7 y = − x + 7
Answer: y = − x + 7 y = -x + 7 y = − x + 7
9. Substitute y = 2 x − 3 y = 2x - 3 y = 2 x − 3 into 3 x + y = 12 3x + y = 12 3 x + y = 12 :
3 x + ( 2 x − 3 ) = 12 3x + (2x - 3) = 12 3 x + ( 2 x − 3 ) = 12
5 x − 3 = 12 5x - 3 = 12 5 x − 3 = 12
5 x = 15 5x = 15 5 x = 15
x = 3 x = 3 x = 3 ✓
y = 2 ( 3 ) − 3 = 3 y = 2(3) - 3 = 3 y = 2 ( 3 ) − 3 = 3 ✓
M1: Correct substitution and solving for x x x
A1: Correct coordinates ( 3 , 3 ) (3, 3) ( 3 , 3 )
Answer: ( 3 , 3 ) (3, 3) ( 3 , 3 )
10. Gradient of E F = 5 − 1 8 − 2 = 4 6 = 2 3 EF = \frac{5 - 1}{8 - 2} = \frac{4}{6} = \frac{2}{3} E F = 8 − 2 5 − 1 = 6 4 = 3 2
For collinearity, gradient of E G EG E G must also be 2 3 \frac{2}{3} 3 2 :
k − 1 4 − 2 = 2 3 \frac{k - 1}{4 - 2} = \frac{2}{3} 4 − 2 k − 1 = 3 2 ✓
k − 1 2 = 2 3 \frac{k - 1}{2} = \frac{2}{3} 2 k − 1 = 3 2
3 ( k − 1 ) = 4 3(k - 1) = 4 3 ( k − 1 ) = 4
3 k − 3 = 4 3k - 3 = 4 3 k − 3 = 4
3 k = 7 3k = 7 3 k = 7
k = 7 3 k = \frac{7}{3} k = 3 7 ✓
M1: Setting up gradient equality
A1: Correct value k = 7 3 k = \frac{7}{3} k = 3 7
Answer: k = 7 3 k = \frac{7}{3} k = 3 7
Section C: Coordinate Geometry Problems (Questions 11–15)
11. (a) A B = ( 5 − 1 ) 2 + ( 8 − 2 ) 2 = 16 + 36 = 52 = 2 13 AB = \sqrt{(5 - 1)^2 + (8 - 2)^2} = \sqrt{16 + 36} = \sqrt{52} = 2\sqrt{13} A B = ( 5 − 1 ) 2 + ( 8 − 2 ) 2 = 16 + 36 = 52 = 2 13 ✓
B C = ( 9 − 5 ) 2 + ( 2 − 8 ) 2 = 16 + 36 = 52 = 2 13 BC = \sqrt{(9 - 5)^2 + (2 - 8)^2} = \sqrt{16 + 36} = \sqrt{52} = 2\sqrt{13} B C = ( 9 − 5 ) 2 + ( 2 − 8 ) 2 = 16 + 36 = 52 = 2 13
Therefore A B = B C AB = BC A B = B C . ✓
M1: Correct distance calculations
A1: Correct conclusion with working
(b) Base A C AC A C : length = 9 − 1 = 8 = 9 - 1 = 8 = 9 − 1 = 8 (horizontal line at y = 2 y = 2 y = 2 )
Height from B B B to A C AC A C : 8 − 2 = 6 8 - 2 = 6 8 − 2 = 6 ✓
Area = 1 2 × 8 × 6 = 24 = \frac{1}{2} \times 8 \times 6 = 24 = 2 1 × 8 × 6 = 24 square units ✓
M1: Identifying base and height
A1: Correct area 24 24 24
Answer: (a) A B = B C = 2 13 AB = BC = 2\sqrt{13} A B = B C = 2 13 (b) 24 24 24 square units
12. (a) For x x x -intercept, set y = 0 y = 0 y = 0 : 2 x − 3 ( 0 ) = 12 ⟹ 2 x = 12 ⟹ x = 6 2x - 3(0) = 12 \implies 2x = 12 \implies x = 6 2 x − 3 ( 0 ) = 12 ⟹ 2 x = 12 ⟹ x = 6 ✓
For y y y -intercept, set x = 0 x = 0 x = 0 : 2 ( 0 ) − 3 y = 12 ⟹ − 3 y = 12 ⟹ y = − 4 2(0) - 3y = 12 \implies -3y = 12 \implies y = -4 2 ( 0 ) − 3 y = 12 ⟹ − 3 y = 12 ⟹ y = − 4 ✓
M1: Correct method for both intercepts
A1: Correct intercepts ( 6 , 0 ) (6, 0) ( 6 , 0 ) and ( 0 , − 4 ) (0, -4) ( 0 , − 4 )
(b) Area = 1 2 × 6 × 4 = 12 = \frac{1}{2} \times 6 \times 4 = 12 = 2 1 × 6 × 4 = 12 square units ✓
A1: Correct area 12 12 12
Answer: (a) x x x -intercept: 6 6 6 , y y y -intercept: − 4 -4 − 4 (b) 12 12 12 square units
13. Since P P P is equidistant from Q ( 2 , 5 ) Q(2, 5) Q ( 2 , 5 ) and R ( 8 , 5 ) R(8, 5) R ( 8 , 5 ) , P P P lies on the perpendicular bisector of Q R QR QR .
Midpoint of Q R QR QR : ( 2 + 8 2 , 5 + 5 2 ) = ( 5 , 5 ) \left(\frac{2 + 8}{2}, \frac{5 + 5}{2}\right) = (5, 5) ( 2 2 + 8 , 2 5 + 5 ) = ( 5 , 5 )
Q R QR QR is horizontal, so perpendicular bisector is vertical line x = 5 x = 5 x = 5 . ✓
P P P also lies on y = 3 x − 1 y = 3x - 1 y = 3 x − 1 .
Substitute x = 5 x = 5 x = 5 : y = 3 ( 5 ) − 1 = 14 y = 3(5) - 1 = 14 y = 3 ( 5 ) − 1 = 14 ✓
Therefore P = ( 5 , 14 ) P = (5, 14) P = ( 5 , 14 ) . ✓
M1: Finding perpendicular bisector of Q R QR QR
M1: Substituting into line equation
A1: Correct coordinates ( 5 , 14 ) (5, 14) ( 5 , 14 )
Answer: ( 5 , 14 ) (5, 14) ( 5 , 14 )
14. (a) Gradient of A B = 2 − 1 5 − 1 = 1 4 AB = \frac{2 - 1}{5 - 1} = \frac{1}{4} A B = 5 − 1 2 − 1 = 4 1 ✓
Gradient of C D = 5 − 6 2 − 6 = − 1 − 4 = 1 4 CD = \frac{5 - 6}{2 - 6} = \frac{-1}{-4} = \frac{1}{4} C D = 2 − 6 5 − 6 = − 4 − 1 = 4 1 ✓
M1: Correct gradient calculations
A1: Both gradients = 1 4 = \frac{1}{4} = 4 1
(b) Gradient of B C = 6 − 2 6 − 5 = 4 1 = 4 BC = \frac{6 - 2}{6 - 5} = \frac{4}{1} = 4 B C = 6 − 5 6 − 2 = 1 4 = 4
Gradient of A D = 5 − 1 2 − 1 = 4 1 = 4 AD = \frac{5 - 1}{2 - 1} = \frac{4}{1} = 4 A D = 2 − 1 5 − 1 = 1 4 = 4
A B ∥ C D AB \parallel CD A B ∥ C D and B C ∥ A D BC \parallel AD B C ∥ A D , so A B C D ABCD A B C D is a parallelogram. ✓✓
M1: Finding remaining gradients
A1: Correct identification with justification
Answer: (a) Both 1 4 \frac{1}{4} 4 1 (b) Parallelogram; both pairs of opposite sides are parallel.
15. Midpoint of ( − 4 , 2 ) (-4, 2) ( − 4 , 2 ) and ( 6 , − 8 ) (6, -8) ( 6 , − 8 ) : ( − 4 + 6 2 , 2 + ( − 8 ) 2 ) = ( 1 , − 3 ) \left(\frac{-4 + 6}{2}, \frac{2 + (-8)}{2}\right) = (1, -3) ( 2 − 4 + 6 , 2 2 + ( − 8 ) ) = ( 1 , − 3 ) ✓
This point lies on y = m x + 3 y = mx + 3 y = m x + 3 :
− 3 = m ( 1 ) + 3 -3 = m(1) + 3 − 3 = m ( 1 ) + 3 ✓
− 3 = m + 3 -3 = m + 3 − 3 = m + 3
m = − 6 m = -6 m = − 6 ✓
M1: Finding midpoint
M1: Substituting into line equation
A1: Correct value m = − 6 m = -6 m = − 6
Answer: m = − 6 m = -6 m = − 6
Section D: Graphs and Coordinate Geometry (Questions 16–20)
16. (a) Plot points ( − 1 , 8 ) (-1, 8) ( − 1 , 8 ) , ( 0 , 3 ) (0, 3) ( 0 , 3 ) , ( 1 , 0 ) (1, 0) ( 1 , 0 ) , ( 2 , − 1 ) (2, -1) ( 2 , − 1 ) , ( 3 , 0 ) (3, 0) ( 3 , 0 ) , ( 4 , 3 ) (4, 3) ( 4 , 3 ) , ( 5 , 8 ) (5, 8) ( 5 , 8 ) and draw smooth parabola. ✓✓
M1: All points plotted correctly
A1: Smooth curve through all points
(b) From graph, curve crosses x x x -axis at x = 1 x = 1 x = 1 and x = 3 x = 3 x = 3 . ✓
A1: Correct solutions x = 1 , 3 x = 1, 3 x = 1 , 3
(c) Draw line y = 2 x − 5 y = 2x - 5 y = 2 x − 5 on same axes (passes through ( 0 , − 5 ) (0, -5) ( 0 , − 5 ) and ( 2.5 , 0 ) (2.5, 0) ( 2.5 , 0 ) ).
Intersection points with parabola: x ≈ − 0.7 x \approx -0.7 x ≈ − 0.7 and x ≈ 4.7 x \approx 4.7 x ≈ 4.7 ✓✓
M1: Drawing correct line
A1: Reading intersection x x x -values correctly (accept − 0.7 -0.7 − 0.7 and 4.7 4.7 4.7 or equivalent)
Answer: (a) Graph (b) x = 1 , 3 x = 1, 3 x = 1 , 3 (c) x ≈ − 0.7 , 4.7 x \approx -0.7, 4.7 x ≈ − 0.7 , 4.7
17. Gradient = 15 − 7 6 − 2 = 8 4 = 2 = \frac{15 - 7}{6 - 2} = \frac{8}{4} = 2 = 6 − 2 15 − 7 = 4 8 = 2 ✓
Equation: y − 7 = 2 ( x − 2 ) y - 7 = 2(x - 2) y − 7 = 2 ( x − 2 )
y − 7 = 2 x − 4 y - 7 = 2x - 4 y − 7 = 2 x − 4
y = 2 x + 3 y = 2x + 3 y = 2 x + 3 ✓
y y y -intercept occurs when x = 0 x = 0 x = 0 : y = 3 y = 3 y = 3 , so point is ( 0 , 3 ) (0, 3) ( 0 , 3 ) . ✓
M1: Finding gradient
M1: Finding equation
A1: Correct coordinates ( 0 , 3 ) (0, 3) ( 0 , 3 )
Answer: ( 0 , 3 ) (0, 3) ( 0 , 3 )
18. Distance = ( 5 − a ) 2 + ( a − 4 ) 2 = 34 = \sqrt{(5 - a)^2 + (a - 4)^2} = \sqrt{34} = ( 5 − a ) 2 + ( a − 4 ) 2 = 34
( 5 − a ) 2 + ( a − 4 ) 2 = 34 (5 - a)^2 + (a - 4)^2 = 34 ( 5 − a ) 2 + ( a − 4 ) 2 = 34 ✓
( 25 − 10 a + a 2 ) + ( a 2 − 8 a + 16 ) = 34 (25 - 10a + a^2) + (a^2 - 8a + 16) = 34 ( 25 − 10 a + a 2 ) + ( a 2 − 8 a + 16 ) = 34
2 a 2 − 18 a + 41 = 34 2a^2 - 18a + 41 = 34 2 a 2 − 18 a + 41 = 34
2 a 2 − 18 a + 7 = 0 2a^2 - 18a + 7 = 0 2 a 2 − 18 a + 7 = 0 ✓
Using quadratic formula: a = 18 ± 324 − 56 4 = 18 ± 268 4 = 18 ± 2 67 4 = 9 ± 67 2 a = \frac{18 \pm \sqrt{324 - 56}}{4} = \frac{18 \pm \sqrt{268}}{4} = \frac{18 \pm 2\sqrt{67}}{4} = \frac{9 \pm \sqrt{67}}{2} a = 4 18 ± 324 − 56 = 4 18 ± 268 = 4 18 ± 2 67 = 2 9 ± 67 ✓
M1: Setting up distance equation
M1: Expanding and simplifying to quadratic
A1: Correct values a = 9 ± 67 2 a = \frac{9 \pm \sqrt{67}}{2} a = 2 9 ± 67
Answer: a = 9 + 67 2 a = \frac{9 + \sqrt{67}}{2} a = 2 9 + 67 or a = 9 − 67 2 a = \frac{9 - \sqrt{67}}{2} a = 2 9 − 67
19. (a) P Q PQ P Q is from ( 0 , 0 ) (0, 0) ( 0 , 0 ) to ( 8 , 0 ) (8, 0) ( 8 , 0 ) , so midpoint of P Q PQ P Q is ( 4 , 0 ) (4, 0) ( 4 , 0 ) . ✓
Median from R ( 4 , 6 ) R(4, 6) R ( 4 , 6 ) to ( 4 , 0 ) (4, 0) ( 4 , 0 ) : vertical line x = 4 x = 4 x = 4 . ✓
M1: Finding midpoint of P Q PQ P Q
A1: Correct equation x = 4 x = 4 x = 4
(b) Base P Q = 8 PQ = 8 P Q = 8 , height = 6 = 6 = 6 (vertical distance from R R R to P Q PQ P Q )
Area = 1 2 × 8 × 6 = 24 = \frac{1}{2} \times 8 \times 6 = 24 = 2 1 × 8 × 6 = 24 square units ✓
A1: Correct area 24 24 24
Answer: (a) x = 4 x = 4 x = 4 (b) 24 24 24 square units
20. (a) Gradient of L 1 = 1 3 L_1 = \frac{1}{3} L 1 = 3 1 , so gradient of L 2 = − 3 L_2 = -3 L 2 = − 3 (perpendicular). ✓
Using point ( 4 , − 1 ) (4, -1) ( 4 , − 1 ) : y − ( − 1 ) = − 3 ( x − 4 ) y - (-1) = -3(x - 4) y − ( − 1 ) = − 3 ( x − 4 )
y + 1 = − 3 x + 12 y + 1 = -3x + 12 y + 1 = − 3 x + 12
y = − 3 x + 11 y = -3x + 11 y = − 3 x + 11 ✓
M1: Finding perpendicular gradient
A1: Correct equation y = − 3 x + 11 y = -3x + 11 y = − 3 x + 11
(b) Intersection: 1 3 x + 2 = − 3 x + 11 \frac{1}{3}x + 2 = -3x + 11 3 1 x + 2 = − 3 x + 11
1 3 x + 3 x = 11 − 2 \frac{1}{3}x + 3x = 11 - 2 3 1 x + 3 x = 11 − 2
10 3 x = 9 \frac{10}{3}x = 9 3 10 x = 9
x = 27 10 = 2.7 x = \frac{27}{10} = 2.7 x = 10 27 = 2.7 ✓
y = 1 3 ( 2.7 ) + 2 = 0.9 + 2 = 2.9 y = \frac{1}{3}(2.7) + 2 = 0.9 + 2 = 2.9 y = 3 1 ( 2.7 ) + 2 = 0.9 + 2 = 2.9
Intersection point: ( 2.7 , 2.9 ) (2.7, 2.9) ( 2.7 , 2.9 ) ✓
M1: Setting equations equal and solving
A1: Correct coordinates ( 2.7 , 2.9 ) (2.7, 2.9) ( 2.7 , 2.9 )
(c) L 1 L_1 L 1 crosses x x x -axis when y = 0 y = 0 y = 0 : 0 = 1 3 x + 2 ⟹ x = − 6 0 = \frac{1}{3}x + 2 \implies x = -6 0 = 3 1 x + 2 ⟹ x = − 6 , point ( − 6 , 0 ) (-6, 0) ( − 6 , 0 ) .
L 2 L_2 L 2 crosses x x x -axis when y = 0 y = 0 y = 0 : 0 = − 3 x + 11 ⟹ x = 11 3 0 = -3x + 11 \implies x = \frac{11}{3} 0 = − 3 x + 11 ⟹ x = 3 11 , point ( 11 3 , 0 ) (\frac{11}{3}, 0) ( 3 11 , 0 ) . ✓
Triangle vertices: ( − 6 , 0 ) (-6, 0) ( − 6 , 0 ) , ( 11 3 , 0 ) (\frac{11}{3}, 0) ( 3 11 , 0 ) , ( 2.7 , 2.9 ) (2.7, 2.9) ( 2.7 , 2.9 ) .
Base = 11 3 − ( − 6 ) = 11 3 + 18 3 = 29 3 = \frac{11}{3} - (-6) = \frac{11}{3} + \frac{18}{3} = \frac{29}{3} = 3 11 − ( − 6 ) = 3 11 + 3 18 = 3 29 ✓
Height = 2.9 = 29 10 = 2.9 = \frac{29}{10} = 2.9 = 10 29
Area = 1 2 × 29 3 × 29 10 = 841 60 ≈ 14.02 = \frac{1}{2} \times \frac{29}{3} \times \frac{29}{10} = \frac{841}{60} \approx 14.02 = 2 1 × 3 29 × 10 29 = 60 841 ≈ 14.02 square units ✓
M1: Finding x x x -intercepts of both lines
M1: Calculating base length
A1: Correct area 841 60 \frac{841}{60} 60 841 or 14.0 14.0 14.0 square units (to 1 d.p.)
Answer: (a) y = − 3 x + 11 y = -3x + 11 y = − 3 x + 11 (b) ( 2.7 , 2.9 ) (2.7, 2.9) ( 2.7 , 2.9 ) (c) 841 60 ≈ 14.0 \frac{841}{60} \approx 14.0 60 841 ≈ 14.0 square units
END OF ANSWER KEY