Question

An alloy of gold and silver weighs 50 gms. It contains 80% gold. How much gold should be added to the alloy so that percentage of gold is increased to 95?

Answer 1

amt of gold present = 80% 0f 50g = 40g
amt. of gold to be added = x
thus .......total gold after addition of x g = 40+x g
a/q
(40+x)/50 * 100= 95%
=> x = 7.5 g (ans.)

Answer 2

Answer:

7.5g gold should be added to the alloy to increase the gold percentage by 95%.

Given, the combined weight of gold and silver = 50 g

The amount of gold present = 80 %

Weight of gold is,

80 % of 50 g =  $\frac{80}{100} \times 50=40 \mathrm{g}$

80 % of gold = 40 g

To make it as 95 %,

95 % of 50 g =  $\frac{95}{100} \times 50=47.5 \mathrm{g}$

47.5 – 40 = 7.5 g  

Hence 7.5 g must be added to make gold as 95%.