A sum of money doubles itself in 4 years at compound interest It will amount to 8 times itself at th...........

Quantitative Aptitude ( CCS) Compound Interest

A sum of money doubles itself in 4 years at compound interest. It will amount to 8 times itself at the same rat of interest in

18 years

12 years

16 years

24 years

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Explanation:

Let Principal =P,
Rate % =R %
t=4 years
∴Amount =2P,
Case1:2 P = P(1+ R/100)^4
2=(1+ R/100)^4..............1
Case2:
Let after t years it will be 8 times
8P = P(1+ R/100)^t
(2)^3 = (1 + R/100)^t...............2
By using eq. 1 and 2
(1+ R/100)^12 = (1 + R/100)^t
By comparing both sides,
t= 12 years