Answer:
The rate of interest will be 40%
Step-by-step explanation:
So first consider the principal to be x
Then the SI (Simple interest) will become six times of itself that is 6x
The time is 15 years
Rate = SI × 100 / P × T
Now put the values
Rate = 6 × x × 100 / x × 15
Then after simplifying the rate will come 40 %
