I deposited 2014 in HDFC bank which gives interest @ 6% per annum. So for how many years I must keep Rs. 2014 in bank so that my money gets doubled (or) comes very near to the doubled amount.
Hint and Directions:
1) Let us assume I had Rs.50 with me on which I am receiving interest at particular rate, after 5 years the amount turns Rs.99.88 and after 6 years it turns up to Rs. 101.
2) Thus according to question the year in which the amount gets doubled or comes nearest to the amount when compared to other years. Hence, the answer will be 5 years and not 6 years because in five years the amount including interest has come very close.
3) The question can be cracked in less than 2 seconds, so better not use calculators!!
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The problem can be cracked by the well-renowned
R U L E O F 7 2
According to rule of 72:
A given amount will be doubled in 72/x years compounded annually where x is the interest provided on the amount.
(it is not applicable with 2% interest rate compounded for 36 years)
Just divide 72 by the interest rate, and you will get the answer as 72/6
= 1 2
Hope, this helps all of you to really learn something new!
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