Correct Answer - Option 2 : 36 gm
Given:
Ratio of Zinc and Copper = 7 : 5
Ratio of Zinc and Copper after adding Zinc = 6 : 3
Calculation:
Let Zinc = 7x and Copper = 5x
According to question:
7x + 5x = 12x
12x = 144
X = 144/12 = 12
Zinc = 7x = 7 × 12 = 84gm
Copper = 5x = 5 × 12 = 60gm
Let Y gm Zinc should be added to make the ratio 6 : 3
⇒ {(84 + Y)/60} = 6/3
⇒ 252 + 3Y = 360
⇒ 3Y = 360 – 252
⇒ 3Y = 108
⇒ Y = 108 / 3 = 36
∴ 36gm Zinc should be added to make the ratio 6 : 3.