an alloy contains iron copper zinc in ratio 3:4:2. another alloy contains copper zinc tin in ratio 10:5:3. If equal quantity is melted then weight of tin per kg in new alloy is?

1/12 kg or 0.0833 kg

83.33gm

ALLOY 1 - Iron = 3x , Copper = 4x , Zinc = 2x ......ALLOY 2 - Copper=10y , Zinc = 5y , Tin = 3y
take LCM of the sum of both ratios (3+4+2 = 9) and (10+5+3=18). So LCM will be 18.
Now consider taking 18kgs of Alloy 1 (consisting 6kg Iron, 8 kg copper, 4 kg zinc) and 18kgs of Alloy 2 (consisting of 10kg copper, 5 kg zinc , 3kg tin).
The ratio of all the metals in combined alloy will be Iron=6kgs , Copper=18kgs , Zinc= 9kgs, Tin= 3kgs.
Weight of Tin per kg in the resultant mixture will be 3/36 kgs i.e. 0.0833 kg.