Question

the simple interest on the sum of money for 5 years at 7% p.a is Rs 800 more than the simple interest on the same sum for 3 years at 9% per annum . find the original sum​

Answer 1

The original sum is Rs. 10000

Step-by-step explanation:

Let the second principal = P

Time = T = 3 years

Rate = R = 9%

Simple interest = S.I = $\frac{PRT}{100} = \frac{P\times 9\times 3}{100}$ = $\frac{27P}{100}$

Let the first principal = P

Time = T = 5 years

Rate = R = 7%

Simple interest = S.I = $\frac{PRT}{100} = \frac{P\times 7\times 5}{100} = \frac{35P}{100}$

The simple interest on the sum of money for 5 years at 7% per annum is Rs. 800 more than the simple interest on the same sum for 3 years at 9% per annum.

So, $\frac{35P}{100} - \frac{27P}{100} = 800$

=> 35P - 27P = 800 x 100 = 80000

=> 8P = 80000

=> P = $\frac{80000}{8}$ = Rs. 10000

Hence, the original sum is Rs. 10000