Question

13. a sum of money invested at compound interest amounts to 800 in 3 years and to 840 in 4 years. The rate of interest per annum is _____.

Answer 1

Explanation:

Given, rate r=5%, n=2 years, compound interest = Rs. 1100

Compound interest = Amount− Principal

Therefore, 1100=P(1+

100

5

)

2

−P

⇒1100=P(1.05)

2

−P

⇒1100=1.1025P−P

⇒P=

0.05

1100

⇒P= Rs. 22000

Simple interest =

100

PRT

=

100

22000×5×2

Simple interest = Rs. 2200