An alloy contains the copper and aluminum in the ratio of 7 : 4 While making the weapons from this alloy, 12% of the alloy got destroyed. If there is 12 kg of aluminum in the weapon, then weight of the alloy required is :

Copper : Aluminum = 7 : 4
Let Copper and Aluminum in the weapon be 7x and 4x respectively
Given,
Aluminum in weapon = 12 kg
So,
→ 4x = 12
→ x = 3
Copper = 7x = 7 × 3 = 21 Kg.
Total alloy in the weapon = 12 + 21 = 33 kg
But 12% alloy get destroyed in making the weapon, i.e. 88% alloy is used in the weapon, so,
→ 88 % alloy = 33 kg
→ 100 % alloy = 37.5 kg