Question

An alloy of gold and copper weights 50 g. It contains 80% gold. How much gold should be added to the alloy so that percentage of gold is increased to 90?

Answer 1

Inital amount of gold = $\frac{8}{10}\times 50$ $=$ $40$gm

Let amount of gold required to me mixed = $X$ gm

According to question ,$40+x=\frac{9}{10}\times$ ($50+x$)

Solving we get $x=50$gm