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  1. A sum of money on compound interest amounts to ₹ 10648 in 3 years and ₹ 9680 in 2 years. The rate of interest per annum is :
    1. 5%
    2. 10%
    3. 15%
    4. 20%
Correct Option: B

Let the sum be ₹ P and rate of interest be R% per annum.
Here , A1 = ₹ 10648 , A2 = ₹ 9680
and t1 = 3 years , t2 = 2 years
Using the given formula ,

A = P1 +
R
n
100

Then,
P1 +
R
2 = 9680    ...(i)
100

P1 +
R
3 = 10648    ...(ii)
100

On dividing equation (ii) by (i)
1 +
R
=
10648
1009680

⇒ 
R
=
10648
− 1
1009680

=
10648 − 9680
9680

⇒ 
R
=
968
=
1
100968010

⇒  R =
1
× 100 = 10%
10



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