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JAMB Mathematics 2017 Paper

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Question : 8

Total: 44

If temperature t is directly proportional to heat h, and when t = 20^oC, h = 50 J, find t when h = 60J

24^oC
20^oC
34^oC
30^oC

Solution:

Concept:

Direct proportion means the ratio of

t

to

h

is constant.

Explanation:

Since

t

is directly proportional to

h

, write

t = kh

, where

k

is the constant of proportionality.

Given

t = 20\,{}^{\circ}\mathrm{C}

when

h = 50\,\mathrm{J}

:

20 = k \times 50

k = \frac{20}{50} = \frac{2}{5}

Now, find

t

when

h = 60\,\mathrm{J}

:

t = \frac{2}{5} \times 60

t = 24\,{}^\circ\mathrm{C}

Answer:

A.

24\,{}^{\circ}\mathrm{C}

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