WAEC Mathematics Past Questions & Answers - Page 137

681.

An arc of a circle subtends an angle of 60o at the centre. If the radius of the circle is 3cm, find , in terms of \(\pi\), the length of the arc

A.

\(\pi\)cm

B.

2\(\pi\)cm

C.

3\(\pi\)cm

D.

6\(\pi\)cm

Correct answer is A

Length of arc = \(\frac{\theta}{360} \times 2\pi r\)

= \(\frac{60}{360} \times 2\pi \times 3cm\)

= \(\pi\)cm

682.

The capacity of a water tank is 1,800 litres. If the tank is in form of a cuboid with base 600cm by 150 cm. Find the height of the tank

A.

2cm

B.

20cm

C.

200cm

D.

2000cm

Correct answer is B

1 litre = 1000cm3

1800 litre = 1800 x 1000cm3

l x b x h = capacity

600 x 150 x h = 1800000

h = \(\frac{1800000}{600 \times 150}\)cm

h = 20cm

683.

If 85% of x is N3230, what is the value of x?

A.

N2745.50

B.

N3714.50

C.

N3800.00

D.

N4845.00

Correct answer is C

85% of x = 3230

\(\frac{85}{100} \times x\) = N3230

x = \(\frac{100}{85}\) x N3230

x = N3800.00

684.

If 92x = \(\frac{1}{3}\)(27x), find x

A.

2

B.

1

C.

-1

D.

-2

Correct answer is C

92x = \(\frac{1}{3}\)(27x)

(22)2x = \(\frac{(3^{3x})}{3}\)

(34x) = 33x - 1

4x = 3x - 1

4x - 3x = -1

x = -1

685.

Express 2.7864 x 10-3 to 2 significant figures

A.

0.28

B.

0.27

C.

0.0028

D.

0.0027

Correct answer is C

2.7864 x 10-3 = 0.0027864

= 0.0028(approx. 2 s.f)