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 90?

• A. 50 gms
• B. 60 gms
• C. 30 gms
• D. 40 gms

Answer 1

The Correct Option is A

Given that the total weight of the alloy is 50 grams and it contains 80% gold, we can first calculate the amount of gold in the alloy:

Amount of gold in the current alloy = 80% of 50 grams = 0.8 × 50 = 40 grams.

Let x be the amount of gold to be added so that the percentage of gold becomes 90%.

After adding x grams of gold, the new total weight of the alloy will be 50 + x grams.

To have 90% gold in the new alloy, the equation becomes:

$\frac{40+x}{50+x}=0.9$

Solving the equation:

Multiply both sides by 50 + x:

40 + x = 0.9(50 + x)

Expand the right side:

40 + x = 45 + 0.9x

Subtract 0.9x from both sides:

40 + 0.1x = 45

Subtract 40 from both sides:

0.1x = 5

Divide by 0.1:

x = 50

Thus, 50 grams of gold should be added to increase the gold content to 90%.