The simple interest on a certain sum for 3 years at 8% per annum is ₹1200. The compound interest on the same sum for 2 years at 10% per annum, compounded annually, is (in ₹):

First recover the sum: $1200=P\times 0.08\times 3=0.24P$ → $P$ = ₹5000. Then the compound interest for 2 years at 10% is $5000(1.1^2-1)=5000\times 0.21$ = ₹1050. (₹1000 is the simple interest for the same 2 years at 10% and leaves out the ₹50 earned on the first year's interest; ₹1655 carries the 3 years across from the first sentence, but the second question runs for 2 years.)