The simple interest received on a sum is 81/100 of the sum. The number of years is equal to the annual rate of interest. What is the annual rate of interest?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 9 %.
The simple interest received on a sum is 81/100 of the sum and the number of years is equal to the annual rate of interest.
Let the principal amount (P) = Rs. 100
So, the simple interest (I) = (81/100) × 100 = Rs. 81
The interest rate (R) = x%
Also, the total time (T) = x years
I = (P × R × T)/100
⇒ 81 = (100 × x × x)/100
⇒ x2 = 81
⇒ x = √81 = 9
Therefore, the annual rate of interest is 9 percent.