Question

At some rate of simple interest, a sum becomes Rs.690 in 3 years and Rs.750 in 5 years. The rate of interest is

Answer 1

S.I for 2 years = ₹ (750-690) = ₹60

Interest for 3 years =  60/2×3 = ₹90

∴ Principal will be = ₹ (690-90) = ₹600

Interest for 5 Years = 60/2×5 = ₹150

∴ Principal will be = ₹ (750-150) = ₹600

As per formula R=(100×S.I)/(P×T) = (100×60)/(600×2) = 5% (ANS)

Answer 2

Sum after 3 years = Rs 690

Sum after 5 years = Rs 750

Find the interest for one year:

Interest for 2 years = 750 - 690 = Rs 60

Interest for 1 year = 60 ÷ 2 = Rs 30

Find the principal:

Interest for 1 year = Rs 30

Interest for 3 years = 30 x 3 = Rs 90

Principal amount = 690 - 90 = Rs 600

Find the interest rate:

Interest rate = interest/principal x 100

Interest rate = 30/600 x 100 = 5%

Answer: The interest rate is 5%