Abhay borrowed Rs. 16000 at 7% per annum simple interest. On the same day, he lent it to Gurmeet at the same rate but compounded annually. What does he gain at the end of 2 years?
Present value = Rs.16000
Interest rate = 7% = (15/2) % per annum
Time = 2 years
Simple interest (SI) = PRT/100 [where, P = Present value
R = Interest rate, T = Time]
∴ SI = (16000 × (15/2) × 2)/100
⇒ SI = 160 × 15
⇒ SI = 2400
Now,
Amount (A) = P (1 + R/100)n [Where, P = Present value
R = Annual interest rate
n = Time in years]
∴ A = 16000 [1 + (15/2)/100]2
⇒ A = 16000 [1 + 3/40]2
⇒ A = 16000 [43/40]2
⇒ A = 16000 × 1849/1600
⇒ A = 10 × 1849
⇒ A = 18490
∴ Amount = Rs.18490
∴ Compound interest = Rs.(18490 – 16000)
= Rs.2490
Now,
(CI – SI) = 2490 -2400
= Rs.90
∴ Abhay gains Rs.90 at the end of 2 years.