# If an amount of Rs.80,000/- was kept in a book for a compound interest

If an amount of Rs.80,000/- was kept in a book for a compound interest at the rate of 10% per year to get an interest of Rs.16,800/-, then the amount was in the bank for a period of

- 3/2 years
- 2 years
- 5/2 years
- 3 years

**Answer: (2) 2 years**

**Solution:-**

Principal = Rs.80,000, Rate = 10%, Compound Interest = Rs.16,800 & Time = ?

**Formula-**

**Compound Interest = {Principal (Rate/100 + 1) ^{Time} – Principal}**

Then, 16,800 = {80,000(10/100 + 1)^{?} – 80,000}

16,800 = 80,000 {(11/10)^{?} – 1}

{(11/10)^{?} – 1} = 16,800/80,000

= 1680/8,000

= 168/800

= 42/200

{(11/10)^{?} – 1} = 21/100

(11/10)^{?} = 21/100 + 1

(11/10)^{?} = 121/100

(11/10)^{?} = (11/10)^{2}

? = 2

Then the amount was in the bank for a period of 2 years.

Hence, the correct answer is option (2) 2 years.