A sum of money invested at simple interest becomes 23/10 of itself in 2 years and 6 months. What is the rate of interest per annum?

Question: A sum of money invested at simple interest becomes 23/10 of itself in 2 years and 6 months. What is the rate of interest per annum?

Solution:
let,
principle = P
interest, I = (23P/10 - P)
= 13P/10
time, n = 2 years 6 months
= 2.5 years
we know,
I = Pnr/100
r = (100 × I)/Pn
= (100 × 13P/10) /P × 2.5
= 52%