Present value of annuity problem?

Question

A payment of Rs. 100 is required to be made at the end of each year for 5 years, after which the value of annual installment increases by Rs. 400 and continued till the end of 10th year. Find the present value of annuity at 3% p.a. How would the answer change if installment 'b' is extended for 40 years?

Answer 1

a) Find the present value of annuity at 3% p.a.

Answer: Rs. 2433.22

How would the answer change if installment 'b' is extended for 40 years?

This is not as clear as it could be. I assume that installment 'a' is 100 and installment 'b' is 500 for five years afterward (10 years in total). If you extend 'b' from 5 to 40 years (45 years in total), the answer is

Rs. 10427.47

There are various ways to calculate this, but the easiest way is by using spreadsheet software (such as MS excel).