Question

The compound interest on a certain sum for 2 years at 5% per annum is Rs 82.
Find the compound interest on the same sum for the same period at 4%.​

Answer 1

Answer:

Principle = 800

Second C.I = 65.28

Step-by-step explanation:

Let the principle = p

Rate = 5% p.a.

Time = 2years

CI = 82

Now,

CI = p × [(1 + r/100)^t - 1]

=> 82 = p × [(1 + 5/100)^2 - 1]

=> 82 = p × [(1 + 1/20)^2 - 1]

=> 82 = p × [(20+1/20)^2 - 1]

=> 82 = p × [(21/20)^2 - 1]

=> 82 = p × [441/400 - 1]

=> 82 = p × [441-400/400]

=> 82 = p × 41/400

=> p = 82 ÷ 41/400

=> p = 82×400/41

=> p = 2×400

=> p = 800

For New C.I.

P = 800

R = 4%p.a

T = 2years

C.I = 800 × [(1 + 4/100)^2 - 1]

= 800 × [(1 + 1/25)^2 - 1]

= 800 × [(25+1/25)^2 - 1]

= 800 × [(26/25)^2 - 1]

= 800 × [676/625 - 1]

= 800 × [676-625/625]

= 800 × 51/625

= 40800/625

= 65.28