Processing math: 40%

WAEC Past Questions and Answers - Page 3899

19,491.

A solid cylinder of radius 7cm is 10 cm long. Find its total surface area.

A.

70πcm2

B.

189πcm2

C.

210πcm2

D.

238πcm2

Correct answer is D

S = 2πr2+2πrh

= 2πr(r+h)

= 2π(7)(7+10)

= 238πcm2

19,492.

The diagram shows a triangular prism of length 7cm. The right - angled triangle PQR is a cross section of the prism |PR| = 5cm and |RQ| = 3cm. What is the volume of the prism?

A.

28cm2

B.

42cm2

C.

70cm2

D.

84cm2

Correct answer is B

Volume of prism = Area x height

In Δ RQP, QR2 + QP2 = RP2

32 + QP2 = 52

QP^2} = 5\(^2 - 32

QP = 16

= 4 cm 

Area = \frac{1}{2} \times base \times height

= \frac{1}{2} \times 3 \times 4

= 6 cm^2

Volume = 6 x 7

= 42 cm^3

19,493.

The diagram shows a triangular prism of length 7cm. The right-angled triangle PQR is a cross-section of the prism |PR| = 5cm and |RQ| = 3cm. What is the area of the cross-section?

A.

4cm2

B.

6cm2

C.

15cm2

D.

20cm2

Correct answer is B

In \Delta RQP, QR^2 + QP^2 = RP^2

3^2 + QP^2 = 5^2

QP^2} = 5\(^2 - 3^2

QP = \sqrt{16}

= 4 cm 

\therefore Area = \frac{1}{2} \times base \times height

= \frac{1}{2} \times 3 \times 4

= 6 cm^2

19,494.

In the diagram, MN||PQ, |LM| = 3cm and |LP| = 4cm. If the area of ∆LMN is 18cm2, find the area of the quadrilateral MPQN

A.

3cm2

B.

6cm2

C.

14cm2

D.

24cm2

Correct answer is C

\frac{LM}{LP} = \frac{3}{4}

\frac{Area of LMN}{Area of LPQ} = \frac{3^2}{4^2}

Area of LPQ = \frac{16}{9}\times 18 = 32 cm^2

Area of quadrilateral MPQN = 32 – 18 = 14 cm^2

19,495.

A sector of a circle radius 14 cm subtends an angle 135° at the center of the circle. What is the perimeter of the sector? Take \pi = \frac{22}{7}

A.

47cm

B.

61cm

C.

88cm

D.

231cm

Correct answer is B

Perimeter of the sector = 2r + \frac{\theta}{360} \times 2\pi r

= 2(14) + \frac{135}{360} \times 2 \times \frac{22}{7} \times 14

= 28 + 33

= 61 cm