Question

a sum of money at simple interest amounts to rupees 800 in 2 years and to rupees 1200 in 2 years the sum is​

Answer 1

The sum of money invested at simple interest is Rs. 600.

• Given,

Amount at S.I. in 2 years = Rs. 800

Amount at S.I. in 6 years = Rs. 1200

• Simple Interest on the sum in 4 years = Amount in 6 years - Amount in 2 years

=> S.I. in 4 years = Rs. 1200 - Rs. 800 = Rs. 400

• Since the S.I. earned in 4 years is Rs. 400, the S.I. earned in each year is equal to Rs. 400 / 4 = Rs. 100

• Now, S.I. earned in 2 years = 2 × Rs. 100 = Rs. 200

• The relationship between a sum of money, simple interest earned on it, and the resultant amount is given by the formula :

Amount = Simple Interest + Principal

• Using the above formula for the amount in 2 years, we get,

Rs. 800 = Rs. 200 + Principal

=> Principal = Rs. 800 - Rs. 200

=> Principal = Rs. 600

∴   The invested sum is Rs. 600.