Zinc and copper are in the ratio 5 : 3 in 400 gm of an alloy.

Zinc and copper are in the ratio 5 : 3 in 400 gm of an alloy. How much of copper (in grams) should be added to make the ratio 5 : 4?

In 400 gm of alloy,

Zinc =	5	× 400 = 250 gm.
	8

Copper =	3	× 400 = 150 gm.
	8

If x gm of copper be mixed, then

250	=	5
150 + x	=	4

⇒ 750 + 5x = 1000
⇒ 5x = 1000 – 750 = 250
⇒ x = 50 gm