A man borrowed 3125 for C.I. which amounted to4500 in 2 years. What was the rate of interest per annum?(A) 30% (B) 25% (C) 20% (D) 15%

To find the rate of interest per annum, we can use the formula for compound interest:

A = P(1 + r/n)^(nt)

Where: A = Final amount (4500) P = Principal amount (3125) r = Rate of interest per annum (unknown) n = Number of times interest is compounded per year (assuming it is compounded annually, n = 1) t = Time in years (2)

Substituting the given values into the formula, we have:

4500 = 3125(1 + r/1)^(1*2)

Simplifying the equation:

4500 = 3125(1 + r)^2

Dividing both sides by 3125:

4500/3125 = (1 + r)^2

1.44 = (1 + r)^2

Taking the square root of both sides:

√1.44 = 1 + r

1.2 = 1 + r

Subtracting 1 from both sides:

0.2 = r

Therefore, the rate of interest per annum is 20%.

So, the correct answer is (C) 20%.