In how many years, Tk. 150 will produce the same interest at 8% as Tk. 800 produce in 3 years at (9/2)%?

Question: In how many years, Tk. 150 will produce the same interest at 8% as Tk. 800 produce in 3 years at (9/2)%?

Solution:
Given,
Principal, P = 800 Tk.
Rate of interest, r = (9/2)%
Time, n = 3 years.
We know,
Interest, I = Pnr
= (800 × 3 × 9)/(2 × 100)
= 108 Tk.

Again,
Principal, P = 150Tk.
Rate of interest, r = 8%
Simple interest, I = 108 Tk.

We know,
I = Pnr
⇒ n = I/Pr
⇒ n = (108 × 100)/(150 × 8)
∴ n = 9 years.