Maths question from Laboratory Attendant exam, 2026 by JKSSB
The compound interest (compounding annually) on a certain sum at the rate of 8 percent per annum for two years is Rs. 6656. What would be the simple interest on the same sum at the same rate of interest for two years?
Last updated Jun 13, 2026
Correct Answer:
Option B —
Rs. 6400
Step-by-Step Breakdown:
Understand Compound Interest for Two Years:
Simple interest remains the same every year because it is only calculated on the original principal amount. Compound interest, however, includes interest earned on the first year's interest.
If the annual rate is 8 percent:
First Year: You get 8 percent of the principal.
Second Year: You get another 8 percent of the principal, plus 8 percent of the first year's interest.
8 percent of 8 percent is 0.64 percent.
Therefore, the total compound interest rate over two years is 8 percent plus 8 percent plus 0.64 percent, which equals 16.64 percent of the principal sum.
Understand Simple Interest for Two Years:
Simple interest for two years is just the annual rate multiplied by two.
8 percent plus 8 percent equals 16 percent of the principal sum.
Relate the Two Values:
We are given that the total compound interest (16.64 percent) is equal to Rs. 6656.
To find what 1 percent of the principal sum is, we divide the total interest by 16.64:
6656 divided by 16.64 equals 400.
So, 1 percent of the sum is equal to Rs. 400.
Calculate the Simple Interest:
Since the simple interest over two years is 16 percent, we simply multiply the value of 1 percent by 16:
400 multiplied by 16 equals Rs. 6400.
Answer verified by Quintessence Classes faculty — Karan Nagar, Srinagar.
