Question

. A sum of money is invested at a half-
yearly compound interest rate of 5% if
the difference of principals at the ends
of 6 months and 12 months be Rs 126
then find, the sum of money invested and the amount at the end of 3/2 years.​

Answer 1

Answer:

Let the principal be P.

Rate of interest per half year = 5%

Amount at the end of 6 months = P(1 + 5/100)

Amount at the end of 1 year = P(1 + 5/100)2

Difference between the amounts

= Rs 126 P(1 + 5/100)2 - P(1 + 5/100)

= 126 P(21/20)2 - P(21/20)

= 126 P(441/400) - P(21/20)

= 126 (441P - 420P) / 400

= 126 21P/400

= 126

P = 2400

So, the sum of money invested is Rs 2400

Amount at the end of 1 and half year = 2400(1 + 5/100)3

= 2400 (21/20)3

= 2400 (9261/8000)

= Rs 2778.30