# 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

1. 3/2 years
2. 2 years
3. 5/2 years
4. 3 years
Anurag Mishra Professor Asked on 19th April 2016 in
1 Answer(s)

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.

Anurag Mishra Professor Answered on 20th April 2016.

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