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1. In an alloy, the ratio of copper and zinc is 5 : 2. If 1.250 kg of zinc is mixed in 17 kg 500 gm of alloy, then the ratio of copper and zinc will be = ?

A. 2 : 1

B. 2 : 3

C. 3 : 2

D. 1 : 2

Solution:

The ratio of copper and zinc is 5 : 2
i.e 5x : 2x
Quantity of initial mixture = 17.5 kg
∴ 5x + 2x =

\frac{35}{2}

⇒ x =

\frac{5}{2}

Quantity of Copper in initial mixture

\begin{aligned} = \frac{5}{2} \times 5 \\ = \frac{25}{2} k g \end{aligned}

Quantity of Zinc in initial mixture

\begin{aligned} = \frac{5}{2} \times 2 \\ = 5 k g \end{aligned}

Now after adding 1.250 kg of zinc
= 5 + 1.250
= 6.250 kg
=

\frac{25}{4} k g

∴ New Ratio of copper : zinc

\begin{aligned} = \frac{25}{2} : \frac{25}{4} \\ = 2 : 1 \end{aligned}

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