Question

A certain sum amounts rs 10400 in 3 years and 12800 in 6 years. find the sum?

Answer 1

Amount in 3 years =10400
Amount in 6 years=12800
Increase in Amount= 12800-10400
=2400
We will subtract this amount from 10400 and thus the sum will be obtained.
10400-2400=8000
Therefore, 8000 is the starting sum.

Answer 2

Solution :-

Principal amount + interest after 6 years = Rs. 12800

Principal amount + interest after 3 years = Rs. 10400

Interest amount of 3 years (i.e. 4th year, 5th year and 6th year) = 12800 - 10400

= Rs. 2400

Hence, Interest amount for 3 years (4th year,5th year and 6th year) is Rs. 2400, then interest amount for first three years (i.e 1st year, 2nd year and 3rd year) will also be Rs. 2400.

Then,

The principal amount = 10400 - 2400

Principal amount = Rs. 8000

Hence, the principal sum invested initially was Rs. 8000

Answer.