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WAEC Mathematics Past Questions & Answers - Page 68

336.

Examine M' $\cap$ N from the venn diagram

{f, g}

{e}

{e, f, g}

View answer & explanation

Correct answer is A

From the venn diagram given,

M = (a, b, c), N = (c, f, g)

U = (a, b, c, d, e, f, g)

Thus M' $\cap$ N = (e, f, g) $\cap$ (c, f, g)

= (f, g)

337.

The perimeter of a sector of a circle of radius 21cm is 64cm. Find the angle of the sector [Take $\pi = \frac{22}{7}$ ]

70^o

60^o

55^o

42^o

View answer & explanation

Correct answer is B

Perimeter of a sector

= 2r + $\frac{\theta}{360^o}$ x 2 x $\frac{22}{7}$ x 21

64 = 2 x 21 + $\frac{\theta}{360^o}$ x 2 x $\frac{22}{7}$ x 21

64 = 42 + $\frac{\theta}{360^o}$ x 44 x 3

64 - 42 = $\frac{\theta}{360^o}$ x 11 x 3

22 = $\frac{33\theta}{90}$

$\theta = \frac{22 \times 30}{11}$

= 60^o

338.

The diagram, MOPQ is a trapezium with QP||MO, MQ||NP, NQ||OP, |QP| = 9cm and the height of $\Delta$ QNP = 6cm, calculate the area of the trapezium.

96cm²

90cm²

81cm²

27cm²

View answer & explanation

Correct answer is C

Area of $\Delta$ QNP = $\frac{1}{2} \times 9 \times 6$ = 27cm²

Area of $\Delta$ QMN = Area of $\Delta$ QNP

= Area of $\Delta$ PNO (triangles between the same parallels)

Hence, area of the trapezium

3 x area of $\Delta$ QNP

= 3 x 27

= 81cm²

339.

Express 1975 correct to 2 significant figures

1,900

1,980

2,000

View answer & explanation

Correct answer is D

No explanation has been provided for this answer.

340.

A sphere of radius rcm has the same volume as cylinder of radius 3cm and height 4cm. Find the value of r

$\frac{2}{3}$

View answer & explanation

Correct answer is C

Volume of sphere = Volume of cylinder

i.e. $\frac{4}{3} \pi r^3 = \pi r^2 h$

$\frac{4}{3} \pi r^3 = \pi \times 3^2 \times 4$

r³ = $\frac{\pi \times 9 \times 4 \times 3}{4 \pi}$

r = 3 $\sqrt{27}$

= 3