Question

On what sum will the compound interest at 15/2 percentage per annum for 3 years compounded annually by ₹3101.40?

Answer 1

Given:
R= 15/2% , n= 3 years

Let the principal be ₹100

Amount (A) = P(1+R/100)^n

A= 100 (1+15/200)^3

A= 100( 1+3/40)^n

A= 100( 43/40)³

A= 100 (79507/64000)

A= 79507/640

A=₹ 124.23

Compound Interest (C.I)= A-P

C.I= 124.23 - 100= ₹24.23


If compound interest is ₹24.23, principal = ₹100

If compound interest is ₹1 , principal= 100/24.23

If compound interest is ₹ 3101.40 ,principal= (100/24.23)× 3101.40

= 310140/24.23= 12799.83

Hence, the sum is= ₹ 12799.83

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Hope this will help you....

Answer 2

Let the principal be 100. Then,

Amount = 100 x (100+15/100x2)^3
=> 100 x (215/200)^3
=> 100 x 43/40 x 43/40 x 43/40
=> 79507/640

Compound Interest = 79507/640 - 100
=> 15507/640

If the C.I is Rs. 15507/640, then principal = 100

If the C.I is Rs. 1, then principal = 100 x 640/15507

If the C.I is Rs. 3101.40, then principal = 100 x 640/15507 x 3101.40 =
Rs. 12800