Question

a sum of rupees 10000 yeilds rs 3310 as compound interest in three years

find the amount

find the rate of interest​​

Answer 1

The final amount is Rs. 10000 and the rate of interest is 10%

• The principal amount is Rs. 10000. Through compound interest it yields Rs. 3310 as compound interest in 36 years.
• So the final amount is the sum of principal and the compound interest. That is 10000 + 3310 = 13310
• Now let the rate of interest is r. Now according to the formula of compound interest we get the equation $10000(1+\frac{r}{100})^{3} = 13310$
• Simplifying it we get $(1+\frac{r}{100})^{3} = \frac{13310}{10000} = \frac{1331}{1000}$

• Taking cube root in both sides we get $1 + \frac{r}{100} = \frac{11}{10}$
• This gives the value of r as 10
• So the final amount is Rs. 10000 and the rate of interest is 10%