An alloy contains the copper and aluminum in the ratio of 7 : 4

Ques - 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 :

a) 48 kg

b) 40 kg

c) 37.5 kg

d) 14.4 kg

Solution -

Copper and Aluminum in the ratio = 7 : 4

Let,

Copper and Aluminum be 7x and 4x respectively in the weapons.

Aluminum in the weapon = 12 kg (given)

4x = 12

x = 3

Therefore,

Copper in the Weapon = 7x

Copper in the weapon = 7*3

Copper in the weapon = 21 kg

Total Alloy in the weapon = 12 + 21

Total Alloy in the weapon = 33 kg

12% of the alloy got destroyed.

Now,

Total alloy in the weapon = (100% - 12%)

Total alloy in the weapon = 88%

But,

Total alloy in the weapon = 33kg 

88%  = 33kg

1% = (33/88)

1% = (3/8)

100% = [(3/8)*100]

100% = 300/8

100% = 37.5

Therefore,

Weight of the alloy required is 37.5

Hence, 

The correct option is (c) 37.5

Thank You