An alloy contains 40 % of silver, 30% of nickel and 30% of copper. How much silver should be added to  25 kg of the alloy so that the new alloy contains 50% of silver?

5

ATQ,

⇒ Silver = \(\frac{25\;×\;4}{100}\) = 10

⇒ Nickal  = \(\frac{25\;×\;3}{10}\) = 7.5

⇒ Copper = \(\frac{25\;×\;3}{10}\) = 7.5

Let x kg silver be added;

⇒ \(\frac{10 + x}{25 + x}\) = \(\frac{50}{100}\)

⇒ 20 + 2x = 25 + x

⇒ x = 5