An alloy contains 30% of copper, 30% of zinc and rest nickel. The amount of nickel in 400 gm of alloy is :

1. 40% of 400 gm

2. 30% of 400 gm

3. 70% of 400 gm

4. 400 gm - 30% of 400 gm

Total weight of alloy = 400gm

Percentage of copper in alloy = 30% of 400gm

Percentage of zinc in alloy = 30% of 400gm

Percentage of copper and zinc in alloy = (30% + 30%) of 400gm

= 60% of 400gm

Percentage of nickel in alloy = (100% - 60%) of 400 gm

= 40% of 400gm

Hence, option 1 is the correct option.