B) If a sum becomes Rs 6,480 in 3 years and Rs 7,776 in 4 years interest compounded annually, find the sum and the rate of interest.

b.my answer is b.

brainliest

8.75

how-to:

first, we need to find what we have to work with.

since i know that we have 7 (years) and 0.8 (inches), we can use these to solve and find the equation!

secondly, what you want to do, is see that we need to know how much growth out of the 0.8 inches he got in only 1 year, instead of 7 years.

let's try to divide.

7 ÷ 0.8 = 8.75