A certain amount was to be distributed among A, B and C in the ratio of 7 : 5 : 3, but due to a mistake the amount was distributed in the ratio of 2 : 3 : 1. As a result of this C got Rs 105 less. What is the difference of the actual share of A and B?

Intended ratio 7:5:3 means A gets 7/15, B gets 5/15, C gets 3/15 of total. Mistaken ratio 2:3:1 means C got 1/6 instead of 3/15 = 1/5. The difference: C got (1/6 - 1/5) less = (5/30 - 6/30) = -1/30 of total. Given C got Rs 105 less: Total × (1/30) = 105, so Total = 3150. Correct shares: A = 7/15 × 3150 = 1470, B = 5/15 × 3150 = 1050. Difference A - B = 1470 - 1050 = 420. Option C is correct.