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

1. 1 : 2

2. 2 : 1

3. 2 : 3

4. 3 : 2

Given,

Total weight of alloy = 17 kg 500 g = 17.5 kg

Given,

Ratio of copper and zinc is 5 : 2.

Let initial quantity of copper be 5x and zinc be 2x.

$\text{Initial quantity of copper} = \dfrac{5x}{5x + 2x} \times 17.5 \\[1em] = \dfrac{5x}{7x} \times 17.5 \\[1em] = 5 \times 2.5 \\[1em] = 12.5\text{ kg} \\[1em] \text{Initial quantity of zinc} = \dfrac{2x}{5x + 2x} \times 17.5 \\[1em] = \dfrac{2x}{7x} \times 17.5 \\[1em] = 2 \times 2.5 \\[1em] = 5\text{ kg}.$

1.250 kg of zinc is mixed in 17 kg 500 g of alloy, so new quantity of zinc = 5 + 1.250 = 6.25 kg.

Ratio of copper to zinc = 12.5 : 6.25 = 2 : 1

Hence, option 2 is the correct option.