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WAEC Mathematics 2018 Paper

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Question : 10

Total: 50

If x : y : z = 3 : 3 : 4, evaluate

\frac{9x+3y}{6z-2y}

1 $\frac{1}{2}$
2
2 $\frac{1}{2}$
3

Solution:

Concept:

A ratio

x : y : z = 3 : 3 : 4

means

x

,

y

, and

z

are proportional to

3

,

3

, and

4

. Assign a common multiplier

k

to each term.

Explanation:

Let

x = 3k

,

y = 3k

, and

z = 4k

.

Substitute these into

\frac{9x+3y}{6z-2y}

.

Numerator:

9x + 3y = 9(3k) + 3(3k)

= 27k + 9k = 36k

Denominator:

6z - 2y = 6(4k) - 2(3k)

= 24k - 6k = 18k

Therefore:

\frac{9x+3y}{6z-2y} = \frac{36k}{18k} = 2

Answer:

2

(Option B)

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