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JAMB Mathematics 2020 Paper

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Question : 25

Total: 40

A school boy lying on the ground 30m away from the foot of a water tank towel observes that the angle of elevation of the top of the tank is 60

^{\circ}

. Calculate the height of the tank.

60 $\sqrt{3m}$
30 $\sqrt{3m}$
20 $\sqrt{3m}$
10 $\sqrt{3m}$

Solution:

Concept:

The height of the tank is found using the tangent ratio in a right-angled triangle.

Explanation:

Let the height of the tank be

h

metres.

The boy is

30

m from the foot of the tank, so the adjacent side is

30

m.

The angle of elevation is

60^\circ

.

Using

\tan \theta = \frac{\text{opposite}}{\text{adjacent}}

:

\tan 60^\circ = \frac{h}{30}

Since

\tan 60^\circ = \sqrt{3}

:

\sqrt{3} = \frac{h}{30}

Multiply both sides by

30

:

h = 30\sqrt{3}

Thus, the height of the tank is

30\sqrt{3}

m.

Answer:

B.

30\sqrt{3}

m

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