Rana took a loan of Tk. 7500 with simple interest for as many years as the rate of interest. If he paid Tk. 1875 as interest at the end of the loan period, what was the rate of interest?

Question: Rana took a loan of Tk. 7500 with simple interest for as many years as the rate of interest. If he paid Tk. 1875 as interest at the end of the loan period, what was the rate of interest?

Solution:
Let,
rate r = R%
and time n = R years

ATQ,
Prn = I
⇒ (7500 × R × R)/100 = 1875
⇒ 75R² = 1875
⇒ R² = 1875/75
⇒ R² = 25
∴ R = 5