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WAEC Mathematics 2018 Paper

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Question : 28

Total: 50

If x : y =

\frac{1}{4} : \frac{3}{8}

\frac{1}{3} : \frac{4}{9}

, find x : z

2:3
3:4
3:8
1:2

Solution:

Concept:

To find

x : z

from the given ratios, combine the ratios by multiplying the two fraction forms.

Explanation:

Given

x : y = \frac{1}{4} : \frac{3}{8}

.

So,

\frac{x}{y} = \frac{1}{4} \div \frac{3}{8} = \frac{1}{4} \times \frac{8}{3} = \frac{2}{3}

.

Also given

y : z = \frac{1}{3} : \frac{4}{9}

.

So,

\frac{y}{z} = \frac{1}{3} \div \frac{4}{9} = \frac{1}{3} \times \frac{9}{4} = \frac{3}{4}

.

Now, multiply these two results to eliminate

y

:

\frac{x}{z} = \frac{x}{y} \times \frac{y}{z} = \frac{2}{3} \times \frac{3}{4} = \frac{2}{4} = \frac{1}{2}

.

Therefore,

x : z = 1 : 2

.

Answer:

x : z = 1 : 2

The correct option is D.

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