Calculation of Annuity using Compound Interest
An annuity is a series of equal payments made at regular intervals. In this case, we are given an annuity of ₹150 for 12 years at a compound interest rate of 3.5% per annum. To calculate the total amount of the annuity, we need to consider the compound interest earned on each payment over the 12-year period.

Formula for Compound Interest
The formula for compound interest is:
A = P(1 + r/n)^(nt)
where:
A = the future value of the investment/loan, including interest
P = the principal investment amount (initial deposit or loan amount)
r = the annual interest rate (decimal)
n = the number of times that interest is compounded per year
t = the number of years the money is invested/borrowed for

Calculation
Given:
P = ₹150 (annuity payment)
r = 3.5% or 0.035
n = 1 (since the interest is compounded annually)
t = 12 years
Plugging in the values:
A = 150(1 + 0.035/1)^(1*12)
A = 150(1.035)^12
A = 150 * 1.4859
A = ₹222.88
Therefore, the total amount of the annuity after 12 years at a compound interest rate of 3.5% per annum is ₹222.88.