Question

a sum of money is invested at compound interest for 9 months at 20%per annum, when the interest is compounded half yearly if the interest were compounded quarterly , it would have fetched Rs 210more than in the previous cas. find the sum

Answer 1

for half yearly AMOUNT=P(1year +half year)
time is 9 mouth
divid 6month and 3 month. R=10 and 5

P(1+10/100)(1+5/100)
P(22/20)(21/20)
for quarterly R=5 time 3 months

P(1+5/100)(1+5/100)(1+5/100)
P(21/20)(21/20)(21/20)
difference is 210
p(21/20)(21/20)(21/20)-p(22/20)(21/20)=210
p(9261/8000)-p(462/400)=210
p(21/8000)=210
p=80000