WAEC Mathematics Past Questions & Answers - Page 157

781.

Each of the interior angle of a regular polygon is 162o. How many sides has the polygon?

A.

8

B.

12

C.

16

D.

20

Correct answer is D

\(\frac{(n - 2)180}{n}\) = 162 (where n = no. of sides)

162n = 180n - 360

162n - 180n = -360

-18n = - 360

n = \(\frac{360}{18}\)

n = 20

782.

Find the volume of a solid cylinder with base radius 10cm and height 14cm.

A.

2203

B.

880cm3>

C.

1400cm3

D.

4400cm3

Correct answer is D

volume of a cylinder = \(\pi r^2h\)

r = 10cm

h = 14cm

= \(\frac{22}{7} \times 10 \times 10 \times 14\)

= 4400cm3

783.

A sector of a circle of radius 14cm containing an angle 60o is folded to form a cone. Calculate the radius of the base of the cone

A.

5\(\frac{1}{2}cm\)

B.

4\(\frac{2}{3}cm\)

C.

3\(\frac{1}{2}cm\)

D.

2\(\frac{1}{3}cm\)

Correct answer is D

Length of arc = circumference of the base of the

cone \(\frac{\theta}{360} \times 2\pi R = 2 \pi r\)

\(\frac{\theta R}{360}\) = r

r = \(\frac{60 \times 14}{360}\)

= \(\frac{7}{3} = 2\frac{1}{3}\)cm

784.

The area of a square field is 110.25m2. Find the cost of fencing it round at N75.00 per metre

A.

N1,575.00

B.

N3,150.00

C.

N4,734.30

D.

N8,268.75

Correct answer is B

Area = 110.252

f2 = 110.25(square)

l = \(\sqrt{110.25}\) = 10.5m

Since N75.00 per metre

N75.00 = 1 metre; x = 10.5m

x = 787.5 for one side, then four sides = N787.5 x 4

= N3,150.00

785.

A chord of length 6cm is drawn in a circle of radius 5cm. Find the distance of the chord from the centre of the circle.

A.

2.5cm

B.

3.0cm

C.

3.5cm

D.

4.0cm

Correct answer is D

Distance(d) = d2 = 52 - 32

= 25 - 9

= 16

d = \(\sqrt{16}\)

= 4cm