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WAEC Mathematics 2023 Paper

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Question : 23

Total: 50

An empty cylindrical tank is 140 cm in diameter. If 200 litres of water was poured into the tank. Calculate, correct to the nearest centimeter, the height of the water in the tank. (

\text{Take } \pi = \frac{22}{7})

91cm
7cm
13cm
57cm

Solution:

Concept:

Use the volume formula for a cylinder,

V = \pi r^2 h

, after converting litres to cubic centimetres.

Explanation:

The tank diameter is

140\text{ cm}

, so its radius is

r = \frac{140}{2} = 70\text{ cm}

.

The volume of water is

200

litres

= 200{,}000\text{ cm}^3

, since

1

litre

= 1000\text{ cm}^3

.

Substitute into

V = \pi r^2 h

:

200{,}000 = \frac{22}{7} \times 70^2 \times h

.

Simplify:

\frac{22}{7} \times 4900 = 15{,}400

.

So,

200{,}000 = 15{,}400 h

.

Thus,

h = \frac{200{,}000}{15{,}400} = 12.987\ldots

cm.

Correct to the nearest centimetre,

h \approx 13\text{ cm}

.

Answer:

C.

13\text{ cm}

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