Question

A certain sum is lent for 3yrs at 10% compound interest p.A. If the
c.I for the 3rd year is 242. Then what will be the s.I for 4yrs

Answer 1

The simple interest for four years will be ₹800.

Given data :

Time = 3 years

Rate = 10%

Compound interest of 3rd year = ₹242

Let,the principal amount = ₹ x

So,the compound interest for first year = x × 10/100 = ₹ x/10

Principal for the second year = (x+x/10) = ₹ 11x/10

Compound interest for the second year = (11x/10 × 10/100) =₹ 11x/100

Principal amount for the third year = 11x/10 + 11x/100 = 110x+11x/100 = ₹ 121x/100

Compound interest of the third year = 121x/100 × 10/100 = ₹ 121x/1000

So,

121x/1000 = 242

x = 242×1000/121

x = 2×1000

x = 2000

So,the principal amount = ₹2000

Now,with the same aspects (principal amount and percentage) the simple interest for four years will be = (2000×10×4)/100 = ₹ 800 (answer)