1. Find the compound interest on Rs.16,000 at 20% per annum for 9 months, compounded quarterly . Please remember, when we have to calculate C.I. quarterly then we apply following formula if n is the number of years Amount=P(1+R4100)4n Principal = Rs.16,000; Time=9 months = 3 quarters; Rate = 20%, it will be 20/4 = 5% So lets solve this question now, Amount=16000(1+5100)3=18522 C.I=18522-16000=2522
2. Sahil took a loan for 6 years at the rate of 5% per annum on Simple Interest, If the total interest paid was Rs. 1230, the principal was S.I.=P*R*T/100
=>P=S.I.*100/R/T By applying above formula we can easily solve this question, as we are already having the simple interest. P = 1230*100/6/5 = 4100
3. A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 854 in 4 years.
The sum is: S.I. for 1 year = Rs. (854 - 815) = Rs. 39. S.I. for 3 years = Rs.(39 x 3) = Rs. 117. Principal = Rs. (815 - 117) = Rs. 698.
4. A certain amount earns simple interest of Rs. 1750 after 7 years. Had the interest been 2% more, how much more interest would it have earned? We need to know the S.I., principal and time to find the rate. Since the principal is not given, so data is inadequate.