Home » Aptitude » Compound Interest » Question
  1. If the amount is 3
    3
    times the sum after 3 years at compound interest
    8
    compounded annually, then the rate of interest per annum is
    1. 25%
    2. 50%
    3. 16
      2
      %
      3
    4. 33
      1
      %
      3
Correct Option: B

Given that , Time = 3 years , Rate = R%
Let Principal be P .

A = P1 +
R
T
100

From the question ,
⇒ 
27
P = P1 +
R
3
8100

⇒ 
3
3 = 1 +
R
3
2100

⇒  1 +
R
=
3
1002

⇒ 
R
=
3
− 1 =
1
10022

⇒  R =
1
× 100
2

∴  R = 50%
Using the given formula :
Here , n =
27
, t = 3 years
8

R% = (n1/n − 1) × 100%
R% =
27
1/3 − 1 × 100
8

R% =
3
− 1 × 100
2

R% =
1
× 100 = 50%
2



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