The compound interest on 15000 at 10% per annum is 3150 Tk. What is the time period?

Question: The compound interest on 15000 at 10% per annum is 3150 Tk. What is the time period?

Solution:
Let the time is = n
C = 15000 + 3150
= 18150 Tk.
r = 10%

we know,
C = P(1 + r)ⁿ
⇒18150 = 15000(1 + 1/10)ⁿ
⇒ 18150/15000 = (11/10)ⁿ
⇒ 121/100 = (11/10)ⁿ
⇒ (11/10)² = (11/10)ⁿ
⇒ n = 2