Answer:
the rate of interest is 9.5% per annum.
Explanation:
To solve this problem, we need to use the formula for compound interest:
A = P(1 + r/n)^(nt)
Where A is the final amount, P is the principal amount, r is the annual interest rate, n is the number of times the interest is compounded per year, and t is the time period.
In this problem, we have P = Rs 4000, A = Rs 4800, n = 1 (interest is compounded annually), and t = 2 years.
Substituting these values into the formula, we get:
4800 = 4000(1 + r/1)^(1*2)
Simplifying the equation, we get:
4800/4000 = (1 + r)^2
1.2 = (1 + r)^2
Taking the square root of both sides, we get:
sqrt(1.2) = 1 + r
r = sqrt(1.2) - 1
r = 0.095
Therefore, the rate of interest is 9.5% per annum.