Question

the difference between the compound interest and the simple interest on a certain sum for 2 years at 5% per annum is rs60. find the sum

Answer 1

IN THE FIRST YEAR

P = Rupees 60
R = 5% / annum
T = 1 years
SI = P×R×T/100
= Rs. ( 60 × 5 × 1 / 100)
= Rs. ( 300/100)
= Rs. 3
Now, Amount = P + SI
Amount = Rs. ( 60+3)
Amount = Rs. 63

IN THE SECOND YEAR

P= Rs. 63
R= 5%
T= 1 year
SI = P×R×T/100
= Rs. ( 63 × 5 × 1 / 100)
= Rs. 315/100
= Rs. 3.15

Now, Compound Interest = P + Si
= Rs. 66.15 ( ans )

Answer 2

let the sum be P = Rs. 100.

time T = 2 years, rate of interest R = 6% per annum

simple interest =  PRT/100= 100*6*2/100=

Rs 12

compound amount= P( 1+R/ 100)^T

= 100*(1+6/100) ^2

= 112.36

therefore the compound interest = compound amount - principal

=112.36-100=12.36/-

the difference between the compound interest and simple interest = 12.36-12.00 = 0.36/-

if the difference between the CI and SI is Rs. 0.36 the principal = Rs. 100

if the difference between the CI and SI is Rs. 90 the principal = 100/0.36*90

= 25000

thus the sum is Rs. 25000.

hope this helps you.