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If x + 0.4y = 3 and y = $\frac{1}{2}$ x, find the value of ...

If x + 0.4y = 3 and y = $\frac{1}{2}$ x, find the value of (x + y)

A.

1 $\frac{1}{4}$

B.

2 $\frac{1}{2}$

C.

3 $\frac{3}{4}$

D.

5

View answer & explanation

Correct answer is C

x + 0.4y = 3...(i)

y = $\frac{1}{2}$ x

x = 2y

x - 2y = 0....(ii)

solve simultaneously; x + 0.4y

= 3 - x - 2y = 0

2.4 = 3

y = $\frac{3 \times 10}{2.4 \times 10}$

= $\frac{30}{24} = \frac{5}{4}$

x - 2( $\frac{5}{4}$ ) = 0

x - $\frac{5}{2}$ = 0

x = $\frac{5}{2}$

x + y = $\frac{5}{2} + \frac{5}{4}$

$\frac{10 + 5}{4} = \frac{15}{4}$

= 3 $\frac{3}{4}$

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