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Secondary 4 Elementary Mathematics Practice Paper 2

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Questions

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TuitionGoWhere Practice Paper - Elementary Mathematics Secondary 4

TuitionGoWhere Practice Paper (AI)
Version: 2 of 5
Subject: Elementary Mathematics (4052)
Level: Secondary 4
Paper: Practice Paper 2 (Geometry & Trigonometry Focus)
Duration: 2 hours 15 minutes
Total Marks: 90

Name: __________________________
Class: __________________________
Date: __________________________


Instructions to Candidates

  1. Write your name, class, and date in the spaces provided at the top of this page.
  2. Answer all questions.
  3. Write your answers in the spaces provided on the question paper.
  4. If working is needed for any question, it must be shown below the question.
  5. The number of marks is given in brackets [ ] at the end of each question or part question.
  6. Give non-exact numerical answers correct to 3 significant figures, or 1 decimal place in the case of angles in degrees, unless a different level of accuracy is specified in the question.
  7. Take π\pi to be 3.1423.142 or use the π\pi key on your calculator.

Section A: Short-Answer Questions (40 Marks)

Answer all questions in this section. Each question carries equal marks unless otherwise stated.

1. In triangle ABCABC, AB=12AB = 12 cm, AC=9AC = 9 cm, and BAC=65\angle BAC = 65^\circ. Calculate the length of BCBC.
<br><br><br> Answer: __________________________ cm [2]

2. The diagram shows a circle with centre OO. TATA and TBTB are tangents to the circle at AA and BB respectively. Angle AOB=110AOB = 110^\circ. Calculate angle ATBATB.
<br><br><br> Answer: __________________________ ^\circ [2]

3. Convert 2.42.4 radians into degrees.
<br><br><br> Answer: __________________________ ^\circ [1]

4. In triangle PQRPQR, PQ=8PQ = 8 cm, QR=10QR = 10 cm, and PQR=40\angle PQR = 40^\circ. Calculate the area of triangle PQRPQR.
<br><br><br> Answer: __________________________ cm2^2 [2]

5. The position vectors of points AA and BB relative to an origin OO are a=(32)\mathbf{a} = \begin{pmatrix} 3 \\ -2 \end{pmatrix} and b=(14)\mathbf{b} = \begin{pmatrix} -1 \\ 4 \end{pmatrix}. Find the magnitude of vector AB\vec{AB}.
<br><br><br> Answer: __________________________ [2]

6. A sector of a circle has a radius of 1515 cm and an angle of 1.21.2 radians. Calculate the area of the sector.
<br><br><br> Answer: __________________________ cm2^2 [2]

7. In the diagram, ABCABC is a triangle. DD lies on ACAC such that BDBD is perpendicular to ACAC. AB=13AB = 13 cm, BD=5BD = 5 cm, and DC=8DC = 8 cm. Calculate angle BCDBCD.
<br><br><br> Answer: __________________________ ^\circ [2]

8. Points A(2,5)A(2, 5) and B(8,1)B(8, 1) are given. Find the gradient of the line perpendicular to ABAB.
<br><br><br> Answer: __________________________ [2]

9. Two similar solids have surface areas of 5050 cm2^2 and 128128 cm2^2. The volume of the smaller solid is 100100 cm3^3. Calculate the volume of the larger solid.
<br><br><br> Answer: __________________________ cm3^3 [3]

10. In triangle XYZXYZ, XYZ=90\angle XYZ = 90^\circ, XY=7XY = 7 cm, and YZ=24YZ = 24 cm. Calculate sin(YXZ)\sin(\angle YXZ). Give your answer as a fraction.
<br><br><br> Answer: __________________________ [2]


Section B: Structured Questions (30 Marks)

Answer all questions in this section.

11. The diagram shows a quadrilateral ABCDABCD.

  • AB=10AB = 10 cm
  • BC=14BC = 14 cm
  • CD=8CD = 8 cm
  • ABC=105\angle ABC = 105^\circ
  • BCD=95\angle BCD = 95^\circ

(a) Calculate the length of diagonal ACAC.
<br><br><br><br> Answer: __________________________ cm [3]

(b) Hence, calculate angle CADCAD, given that AD=12AD = 12 cm.
<br><br><br><br> Answer: __________________________ ^\circ [3]

12. The diagram shows a pyramid with a rectangular base ABCDABCD. The vertex VV is vertically above the centre MM of the base.

  • AB=10AB = 10 cm
  • BC=8BC = 8 cm
  • VM=12VM = 12 cm

(a) Calculate the length of the diagonal ACAC of the base.
<br><br><br><br> Answer: __________________________ cm [2]

(b) Calculate the angle between the edge VAVA and the base ABCDABCD.
<br><br><br><br> Answer: __________________________ ^\circ [3]

(c) Calculate the total surface area of the pyramid.
<br><br><br><br> Answer: __________________________ cm2^2 [4]

13. Points AA, BB, and CC lie on a circle with centre OO. The line DTDT is a tangent to the circle at CC.

  • AOC=130\angle AOC = 130^\circ
  • OCB=25\angle OCB = 25^\circ

(a) Find OAC\angle OAC.
<br><br><br><br> Answer: __________________________ ^\circ [2]

(b) Find ACB\angle ACB.
<br><br><br><br> Answer: __________________________ ^\circ [2]

(c) Find ACD\angle ACD.
<br><br><br><br> Answer: __________________________ ^\circ [2]

14. A ship sails from Port PP on a bearing of 050050^\circ for 4040 km to Point QQ. It then changes course and sails on a bearing of 140140^\circ for 3030 km to Point RR.

(a) Calculate the distance PRPR.
<br><br><br><br> Answer: __________________________ km [3]

(b) Calculate the bearing of PP from RR.
<br><br><br><br> Answer: __________________________ ^\circ [4]


Section C: Problem Solving (20 Marks)

Answer all questions in this section.

15. The diagram shows a triangle ABCABC inscribed in a circle. ABAB is a diameter of the circle. DD is a point on the circumference such that CDCD is parallel to ABAB.

  • CAB=35\angle CAB = 35^\circ

(a) State the value of ACB\angle ACB, giving a reason.
<br><br> Reason: _________________________________________________________________
Answer: __________________________ ^\circ [2]

(b) Calculate ABC\angle ABC.
<br><br><br> Answer: __________________________ ^\circ [1]

(c) Calculate BCD\angle BCD.
<br><br><br> Answer: __________________________ ^\circ [2]

(d) Prove that triangle ADCADC is congruent to triangle BCDBCD.
<br><br><br><br><br> [3]

16. A garden is in the shape of a sector of a circle with radius 2020 m and angle 120120^\circ. A fence is built along the arc and the two radii.

(a) Calculate the length of the arc.
<br><br><br> Answer: __________________________ m [2]

(b) Calculate the total length of the fence.
<br><br><br> Answer: __________________________ m [1]

(c) The garden is to be covered with grass turf. Each roll of turf covers 55 m2^2. Calculate the minimum number of rolls required.
<br><br><br> Answer: __________________________ [3]

(d) A path is constructed from the centre of the circle to the midpoint of the arc. Calculate the area of the segment cut off by the chord connecting the ends of the radii.
<br><br><br><br> Answer: __________________________ m2^2 [4]

17. In triangle ABCABC, AB=cAB = c, BC=aBC = a, and AC=bAC = b. (a) Write down the Cosine Rule for side aa.
<br><br> Answer: __________________________ [1]

(b) Hence, show that if a2+b2=c2a^2 + b^2 = c^2, then angle C=90C = 90^\circ.
<br><br><br><br><br> [2]

(c) In a specific triangle, a=5a=5, b=7b=7, and c=8c=8. Calculate the size of the largest angle.
<br><br><br> Answer: __________________________ ^\circ [3]

18. The diagram shows two triangles, ABEABE and DCEDCE. ABAB is parallel to DCDC.

  • AB=12AB = 12 cm
  • DC=8DC = 8 cm
  • BE=9BE = 9 cm

(a) Explain why triangle ABEABE is similar to triangle DCEDCE.
<br><br><br><br> [2]

(b) Calculate the length of CECE.
<br><br><br> Answer: __________________________ cm [2]

(c) The area of triangle DCEDCE is 2424 cm2^2. Calculate the area of triangle ABEABE.
<br><br><br> Answer: __________________________ cm2^2 [2]

19. A ladder of length 55 m leans against a vertical wall. The foot of the ladder is 1.51.5 m from the base of the wall.

(a) Calculate the angle the ladder makes with the horizontal ground.
<br><br><br> Answer: __________________________ ^\circ [2]

(b) The foot of the ladder is pulled away from the wall by 0.50.5 m. Calculate how far down the wall the top of the ladder slides.
<br><br><br><br> Answer: __________________________ m [3]

20. Points A(1,2)A(1, 2), B(5,6)B(5, 6), and C(9,2)C(9, 2) form a triangle.

(a) Show that triangle ABCABC is isosceles.
<br><br><br><br> [3]

(b) Find the coordinates of the midpoint MM of ACAC.
<br><br><br> Answer: __________________________ [1]

(c) Calculate the area of triangle ABCABC.
<br><br><br> Answer: __________________________ units2^2 [2]


End of Paper

Answers

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TuitionGoWhere Practice Paper - Elementary Mathematics Secondary 4

Answer Key & Marking Scheme (Version 2)

Subject: Elementary Mathematics
Topic: Geometry & Trigonometry


Section A: Short-Answer Questions

1. Length of BCBC
Using Cosine Rule: a2=b2+c22bccosAa^2 = b^2 + c^2 - 2bc \cos A
BC2=92+1222(9)(12)cos65BC^2 = 9^2 + 12^2 - 2(9)(12) \cos 65^\circ
BC2=81+144216(0.4226)BC^2 = 81 + 144 - 216(0.4226)
BC2=22591.28=133.72BC^2 = 225 - 91.28 = 133.72
BC=133.7211.56BC = \sqrt{133.72} \approx 11.56
Answer: 11.6 cm [2]
(1 mark for correct substitution, 1 mark for answer)

2. Angle ATBATB
Tangents are perpendicular to radius: OAT=OBT=90\angle OAT = \angle OBT = 90^\circ.
Quadrilateral OATBOATB: Sum of angles = 360360^\circ.
ATB=3609090110=70\angle ATB = 360^\circ - 90^\circ - 90^\circ - 110^\circ = 70^\circ.
Answer: 70^\circ [2]

3. Radians to Degrees
2.4×180π=2.4×57.295...137.512.4 \times \frac{180}{\pi} = 2.4 \times 57.295... \approx 137.51
Answer: 138^\circ (or 137.5^\circ) [1]

4. Area of Triangle PQRPQR
Area =12absinC= \frac{1}{2} ab \sin C
Area =12(8)(10)sin40= \frac{1}{2} (8)(10) \sin 40^\circ
Area =40×0.642825.71= 40 \times 0.6428 \approx 25.71
Answer: 25.7 cm2^2 [2]

5. Magnitude of AB\vec{AB}
AB=ba=(14)(32)=(46)\vec{AB} = \mathbf{b} - \mathbf{a} = \begin{pmatrix} -1 \\ 4 \end{pmatrix} - \begin{pmatrix} 3 \\ -2 \end{pmatrix} = \begin{pmatrix} -4 \\ 6 \end{pmatrix}
AB=(4)2+62=16+36=527.21|\vec{AB}| = \sqrt{(-4)^2 + 6^2} = \sqrt{16 + 36} = \sqrt{52} \approx 7.21
Answer: 7.21 [2]

6. Area of Sector (Radians)
Area =12r2θ= \frac{1}{2} r^2 \theta
Area =12(15)2(1.2)=12(225)(1.2)=135= \frac{1}{2} (15)^2 (1.2) = \frac{1}{2} (225)(1.2) = 135
Answer: 135 cm2^2 [2]

7. Angle BCDBCD
In BDC\triangle BDC (right-angled at DD):
First find BDBD? No, BDBD is given as 5. Wait, BDACBD \perp AC.
In right ABD\triangle ABD: AD=13252=16925=12AD = \sqrt{13^2 - 5^2} = \sqrt{169-25} = 12.
This is not needed for BCD\angle BCD.
In right BDC\triangle BDC: tan(BCD)=BDDC=58\tan(\angle BCD) = \frac{BD}{DC} = \frac{5}{8}.
BCD=tan1(0.625)32.0\angle BCD = \tan^{-1}(0.625) \approx 32.0^\circ.
Answer: 32.0^\circ [2]

8. Gradient of Perpendicular
Gradient AB=1582=46=23AB = \frac{1-5}{8-2} = \frac{-4}{6} = -\frac{2}{3}.
Gradient perpendicular =1m=12/3=32= -\frac{1}{m} = -\frac{1}{-2/3} = \frac{3}{2}.
Answer: 1.5 (or 32\frac{3}{2}) [2]

9. Volume of Larger Solid
Ratio of Areas =50:128=25:64= 50 : 128 = 25 : 64.
Linear Scale Factor k=6425=85=1.6k = \sqrt{\frac{64}{25}} = \frac{8}{5} = 1.6.
Volume Scale Factor =k3=1.63=4.096= k^3 = 1.6^3 = 4.096.
Volume Larger =100×4.096=409.6= 100 \times 4.096 = 409.6.
Answer: 410 cm3^3 (3 s.f.) [3]

10. sin(YXZ)\sin(\angle YXZ)
Hypotenuse XZ=72+242=49+576=625=25XZ = \sqrt{7^2 + 24^2} = \sqrt{49 + 576} = \sqrt{625} = 25.
sin(YXZ)=OppositeHypotenuse=YZXZ=2425\sin(\angle YXZ) = \frac{\text{Opposite}}{\text{Hypotenuse}} = \frac{YZ}{XZ} = \frac{24}{25}.
Answer: 2425\frac{24}{25} [2]


Section B: Structured Questions

11. Quadrilateral ABCDABCD

(a) Length ACAC
In ABC\triangle ABC:
AC2=102+1422(10)(14)cos105AC^2 = 10^2 + 14^2 - 2(10)(14) \cos 105^\circ
AC2=100+196280(0.2588)AC^2 = 100 + 196 - 280(-0.2588)
AC2=296+72.46=368.46AC^2 = 296 + 72.46 = 368.46
AC=368.4619.195AC = \sqrt{368.46} \approx 19.195
Answer: 19.2 cm [3]

(b) Angle CADCAD
In ACD\triangle ACD: Sides are AC19.2AC \approx 19.2, CD=8CD = 8, AD=12AD = 12.
Use Cosine Rule for CAD\angle CAD (let CAD=A\angle CAD = A):
CD2=AC2+AD22(AC)(AD)cosACD^2 = AC^2 + AD^2 - 2(AC)(AD) \cos A
82=19.1952+1222(19.195)(12)cosA8^2 = 19.195^2 + 12^2 - 2(19.195)(12) \cos A
64=368.45+144460.68cosA64 = 368.45 + 144 - 460.68 \cos A
64=512.45460.68cosA64 = 512.45 - 460.68 \cos A
460.68cosA=448.45460.68 \cos A = 448.45
cosA=0.9734\cos A = 0.9734
A=cos1(0.9734)13.25A = \cos^{-1}(0.9734) \approx 13.25^\circ
Answer: 13.3^\circ [3]

12. Pyramid VABCDVABCD

(a) Diagonal ACAC
AC=102+82=100+64=16412.806AC = \sqrt{10^2 + 8^2} = \sqrt{100 + 64} = \sqrt{164} \approx 12.806
Answer: 12.8 cm [2]

(b) Angle between VAVA and Base
Let MM be centre of base. AM=12AC=6.403AM = \frac{1}{2} AC = 6.403 cm.
VMA\triangle VMA is right-angled at MM.
tan(VAM)=VMAM=126.4031.874\tan(\angle VAM) = \frac{VM}{AM} = \frac{12}{6.403} \approx 1.874
VAM=tan1(1.874)61.9\angle VAM = \tan^{-1}(1.874) \approx 61.9^\circ
Answer: 61.9^\circ [3]

(c) Total Surface Area
Base Area =10×8=80= 10 \times 8 = 80 cm2^2.
Slant height of triangular faces:
For face VABVAB: Height h1h_1 from VV to midpoint of ABAB. Distance from MM to ABAB is 44 cm.
h1=122+42=144+16=16012.649h_1 = \sqrt{12^2 + 4^2} = \sqrt{144+16} = \sqrt{160} \approx 12.649 cm.
Area VAB=12×10×12.649=63.245VAB = \frac{1}{2} \times 10 \times 12.649 = 63.245 cm2^2.
For face VBCVBC: Height h2h_2 from VV to midpoint of BCBC. Distance from MM to BCBC is 55 cm.
h2=122+52=144+25=169=13h_2 = \sqrt{12^2 + 5^2} = \sqrt{144+25} = \sqrt{169} = 13 cm.
Area VBC=12×8×13=52VBC = \frac{1}{2} \times 8 \times 13 = 52 cm2^2.
Total Area =80+2(63.245)+2(52)=80+126.49+104=310.49= 80 + 2(63.245) + 2(52) = 80 + 126.49 + 104 = 310.49
Answer: 310 cm2^2 (3 s.f.) [4]

13. Circle Geometry

(a) OAC\angle OAC
OAC\triangle OAC is isosceles (OA=OCOA=OC radii).
AOC=130\angle AOC = 130^\circ.
OAC=1801302=25\angle OAC = \frac{180 - 130}{2} = 25^\circ.
Answer: 25^\circ [2]

(b) ACB\angle ACB
Angle at centre AOB\angle AOB? No, we need ACB\angle ACB.
Wait, AOC=130\angle AOC = 130^\circ. Reflex AOC=230\angle AOC = 230^\circ? No.
Angle at circumference ABC=12AOC=65\angle ABC = \frac{1}{2} \angle AOC = 65^\circ.
This doesn't give ACB\angle ACB directly.
Let's use OBC\triangle OBC. OB=OCOB=OC radii.
We are given OCB=25\angle OCB = 25^\circ. So OBC=25\angle OBC = 25^\circ.
BOC=1802525=130\angle BOC = 180 - 25 - 25 = 130^\circ.
Angles at centre: AOB=360130130=100\angle AOB = 360 - 130 - 130 = 100^\circ.
OAB\triangle OAB is isosceles. OBA=OAB=1801002=40\angle OBA = \angle OAB = \frac{180-100}{2} = 40^\circ.
ACB\angle ACB subtends arc ABAB. Angle at centre AOB=100\angle AOB = 100^\circ.
ACB=12(100)=50\angle ACB = \frac{1}{2} (100) = 50^\circ.
Answer: 50^\circ [2]

(c) ACD\angle ACD
Tangent DTDT at CC. Radius OCDTOC \perp DT. OCD=90\angle OCD = 90^\circ? No, DD is on tangent line.
Angle between tangent and chord ACAC: ACD\angle ACD?
Alternate Segment Theorem: Angle between tangent and chord equals angle in alternate segment.
Chord ACAC. Angle in alternate segment is ABC\angle ABC.
ABC=ABO+OBC=40+25=65\angle ABC = \angle ABO + \angle OBC = 40^\circ + 25^\circ = 65^\circ.
So ACD=65\angle ACD = 65^\circ.
Alternatively: OCD=90\angle OCD = 90^\circ. OCA=25\angle OCA = 25^\circ (from part a, base angle of isosceles OAC\triangle OAC).
ACD=9025=65\angle ACD = 90 - 25 = 65^\circ.
Answer: 65^\circ [2]

14. Bearings

(a) Distance PRPR
Bearing PQ=050P \to Q = 050^\circ. Bearing QR=140Q \to R = 140^\circ.
Angle inside PQR\triangle PQR at QQ:
North at QQ is parallel to North at PP.
Back bearing QP=050+180=230Q \to P = 050 + 180 = 230^\circ.
Angle PQR=230140=90PQR = 230 - 140 = 90^\circ.
So PQR\triangle PQR is right-angled.
PR=402+302=1600+900=2500=50PR = \sqrt{40^2 + 30^2} = \sqrt{1600 + 900} = \sqrt{2500} = 50.
Answer: 50 km [3]

(b) Bearing of PP from RR
In right PQR\triangle PQR: tan(PRQ)=4030\tan(\angle PRQ) = \frac{40}{30}.
PRQ=tan1(43)53.13\angle PRQ = \tan^{-1}(\frac{4}{3}) \approx 53.13^\circ.
Bearing QRQ \to R is 140140^\circ.
Back bearing RQR \to Q is 140+180=320140 + 180 = 320^\circ.
Bearing RP=32053.13=266.87R \to P = 320 - 53.13 = 266.87^\circ.
Answer: 267^\circ [4]


Section C: Problem Solving

15. Circle Properties

(a) ACB\angle ACB
Angle in a semicircle is 9090^\circ.
Answer: 90^\circ [2]

(b) ABC\angle ABC
In ABC\triangle ABC: 1809035=55180 - 90 - 35 = 55^\circ.
Answer: 55^\circ [1]

(c) BCD\angle BCD
ABCDAB \parallel CD. Alternate interior angles? No, BCBC is transversal.
ABC=BCD\angle ABC = \angle BCD (Alternate angles)? Yes, if ABCDAB \parallel CD.
So BCD=55\angle BCD = 55^\circ.
Answer: 55^\circ [2]

(d) Congruence ADCBCD\triangle ADC \cong \triangle BCD

  1. CDCD is common side.
  2. AD=BCAD = BC? In isosceles trapezium (parallel chords intercept equal arcs), yes. Or:
    DAC=DBC\angle DAC = \angle DBC (angles in same segment).
    ACD=BDC\angle ACD = \angle BDC (alternate angles to CAB\angle CAB and DBA\angle DBA? No).
    Better proof:
    ABCD    AB \parallel CD \implies Arc AD=AD = Arc BC    BC \implies Chord AD=AD = Chord BCBC.
    AC=BDAC = BD (diagonals of isosceles trapezium).
    CDCD common.
    SSS Congruence.
    [3 marks for valid reasoning]

16. Sector Garden

(a) Arc Length
Angle =120=120360×2πr=13×2π(20)=40π341.89= 120^\circ = \frac{120}{360} \times 2\pi r = \frac{1}{3} \times 2 \pi (20) = \frac{40\pi}{3} \approx 41.89 m.
Answer: 41.9 m [2]

(b) Total Fence
Perimeter =Arc+2r=41.89+40=81.89= \text{Arc} + 2r = 41.89 + 40 = 81.89 m.
Answer: 81.9 m [1]

(c) Turf Rolls
Area Sector =120360π(20)2=13π(400)418.88= \frac{120}{360} \pi (20)^2 = \frac{1}{3} \pi (400) \approx 418.88 m2^2.
Rolls =418.885=83.77= \frac{418.88}{5} = 83.77.
Must buy whole rolls.
Answer: 84 rolls [3]

(d) Segment Area
Area Segment =Area SectorArea Triangle= \text{Area Sector} - \text{Area Triangle}.
Area Triangle =12r2sin(120)=12(400)(0.866)=173.2= \frac{1}{2} r^2 \sin(120^\circ) = \frac{1}{2} (400) (0.866) = 173.2 m2^2.
Area Segment =418.88173.2=245.68= 418.88 - 173.2 = 245.68 m2^2.
Answer: 246 m2^2 [4]

17. Cosine Rule Derivation

(a) Formula
a2=b2+c22bccosAa^2 = b^2 + c^2 - 2bc \cos A. [1]

(b) Proof
If a2+b2=c2a^2 + b^2 = c^2, substitute into Cosine Rule for cc:
c2=a2+b22abcosCc^2 = a^2 + b^2 - 2ab \cos C.
a2+b2=a2+b22abcosCa^2 + b^2 = a^2 + b^2 - 2ab \cos C.
0=2abcosC    cosC=0    C=900 = -2ab \cos C \implies \cos C = 0 \implies C = 90^\circ. [2]

(c) Largest Angle
Largest angle is opposite longest side (c=8c=8).
cosC=52+72822(5)(7)=25+496470=1070=17\cos C = \frac{5^2 + 7^2 - 8^2}{2(5)(7)} = \frac{25 + 49 - 64}{70} = \frac{10}{70} = \frac{1}{7}.
C=cos1(1/7)81.8C = \cos^{-1}(1/7) \approx 81.8^\circ.
Answer: 81.8^\circ [3]

18. Similar Triangles

(a) Similarity
ABE=DCE\angle ABE = \angle DCE (Alternate angles, ABDCAB \parallel DC).
BAE=CDE\angle BAE = \angle CDE (Alternate angles).
AEB=DEC\angle AEB = \angle DEC (Vertically opposite).
AAA Similarity. [2]

(b) Length CECE
Scale Factor =DCAB=812=23= \frac{DC}{AB} = \frac{8}{12} = \frac{2}{3}.
CE=23BE=23(9)=6CE = \frac{2}{3} BE = \frac{2}{3} (9) = 6 cm.
Answer: 6 cm [2]

(c) Area ABEABE
Area Scale Factor =(Linear SF)2=(32)2=2.25= (\text{Linear SF})^2 = (\frac{3}{2})^2 = 2.25 (from small to large).
Area ABE=24×2.25=54ABE = 24 \times 2.25 = 54 cm2^2.
Answer: 54 cm2^2 [2]

19. Ladder Problem

(a) Angle with Ground
cosθ=1.55=0.3\cos \theta = \frac{1.5}{5} = 0.3.
θ=cos1(0.3)72.54\theta = \cos^{-1}(0.3) \approx 72.54^\circ.
Answer: 72.5^\circ [2]

(b) Slide Down
Initial height h1=521.52=252.25=22.754.77h_1 = \sqrt{5^2 - 1.5^2} = \sqrt{25 - 2.25} = \sqrt{22.75} \approx 4.77 m.
New base =1.5+0.5=2.0= 1.5 + 0.5 = 2.0 m.
New height h2=5222=254=214.58h_2 = \sqrt{5^2 - 2^2} = \sqrt{25 - 4} = \sqrt{21} \approx 4.58 m.
Slide =4.774.58=0.19= 4.77 - 4.58 = 0.19 m.
Answer: 0.19 m [3]

20. Coordinate Geometry

(a) Isosceles Proof
AB=(51)2+(62)2=16+16=32AB = \sqrt{(5-1)^2 + (6-2)^2} = \sqrt{16+16} = \sqrt{32}.
BC=(95)2+(26)2=16+16=32BC = \sqrt{(9-5)^2 + (2-6)^2} = \sqrt{16+16} = \sqrt{32}.
AB=BCAB = BC, so isosceles. [3]

(b) Midpoint MM
M=(1+92,2+22)=(5,2)M = (\frac{1+9}{2}, \frac{2+2}{2}) = (5, 2).
Answer: (5,2)(5, 2) [1]

(c) Area
Base ACAC is horizontal. Length =91=8= 9 - 1 = 8.
Height =yByM=62=4= y_B - y_M = 6 - 2 = 4.
Area =12×8×4=16= \frac{1}{2} \times 8 \times 4 = 16.
Answer: 16 units2^2 [2]