Question

$50$ $g$ of an alloy of gold and silver contains $80$ $\%$ gold(by weight). The quantity of gold, that is to be mixed up with this alloy, so that it may contain $95$ $\%$ gold, is:

• A. $200$ $g$
• B. $150$ $g$
• C. $50$ $g$
• D. $10$ $g$

Answer 1

The correct option is B $150$ $g$

$50g$ of gold contains $80$% of gold.

Hence amount of gold $=\frac{80}{100}\times 50=\frac{80}{2}=40g$

So, $\frac{40+x}{50+x}=\frac{95}{100}=\frac{19}{20}$

$20(40+x)=19(50+x)$

$800+20x=950+19x$

$20x-19x=950-800$

$x=150g$