Question

The sum of money at simple interest amounts to rs. 815 in 3 years and rs. 854 in 4 years. Find the original sum.

Answer 1

A sum of money at simple interest amounts to 815 in 3 years and to 854 in 4 years.

Interest for 1 year = 854-815= Rs 39.

Interest for 3 years = 39*3= 117

sum = 815-117 = Rs. 698

Answer 2

$\huge\blue{Answer\:is}$

As this is simple intrest the intrest in each year wiil same.
ex if sum is 900 an simple intrest is rs 20
then 
first year SI amount is 900+20=920
2nd year SI =920+20=940....
3rd year Si=940+20=960
by looking the above we can easily get the simple intrest i.e 960-940=20...
so acc to question 3 yr SI=815
4 yr SI=854
so intrest=854-815=39
for 1 yr it  is39
for 3 yr 39X3=117
so sum(Principle)=815-117=698


hope u got it.....