Question

An alloy of gold and silver contains 80% gold by weight. In 50 g of this alloy. How much silver should be added to make it an alloy with 75% gold ?
1. 2.5 g
2. \(\dfrac{10}{3}\ g\)
3. 5 g
4. \(\dfrac{16}{3} \ g\)

Answer 1

Correct Answer - Option 2 : \(\dfrac{10}{3}\ g\)

Given:

Gold in the alloy is 80%

Calculation:

The quantity of gold in 50g of alloy

50 × 80/100 = 40g

The quantity of gold changed to 75%

75% = 40g

⇒ 100% = (40/75) × 100 = 160/3

Quantity added

\(\frac{160}{3} \ - \ 50\)

⇒ \(\frac{160 \ - \ 150}{3} \) = \(\frac{10}{3} \)g

∴ The \(\frac{10}{3} \)g will be added.