Question

In what time will the interest on a certain sum of money at 7% be 11/ 4 ( 2 whole 3 / 4 ) of itself ?


Please answer fast .
please answer with explanation .
I' ll mark brainliest answer if it will be correct .
( The answer in my answer sheet is 25 years , it want the whole solution )​

Answer 1

{ The answer can come 25 years only when the rate of interest is 11% per year. }

Step-by-step explanation:

Let us consider that the certain sum of money be of Rs. P and the time of investment be T years, which to be computed at 11% simple rate per year. Let I be the interest.

If I be the interest in T years,

I = Ptr/100,

where r = rate of interest p.a.

Given, I = 11/4 * P = 11P/4, r = 11%

Then 11P/4 = PT * 11/100

or, 11/4 = 11T/100

or, T = 100/4

or, T = 25

Therefore the time of investment is 25 years.

Answer 2

Answer:

Step-by-step explanation:

Let say it happens after  n years

Case 1 : Compound interest  Annually -

Then Interest = P * (1  + 7/100)ⁿ -  P

Interest = 11P/4

11P/4  = P * (1  + 7/100)ⁿ -  P

=> 15P/4  =  P * (1  + 7/100)ⁿ

=>  (1.07)ⁿ  = 15/4

Taking log both sides

=> n log(1.07) = log(15/4)

=>  n = 19.5 years

Case 2 Simple Interest

11P/4  = P *  7  * n /100

=> n = 1100/28

=> n = 39.3 Years

Case  3  : Amount becomes = 11P/4 after n years at simple interest

then interest = 11P/4 - P = 7P/4

7P/4  = P * 7 * n/100

=> n = 25 years

So correct Question Should be

In what time will the amount on a certain sum of money at 7% (simple interest) be 11/ 4 ( 2 whole 3 / 4 ) of itself