Quantitative Aptitude Ques 2269
Question: sum of money doubles itself at compound interest in 15 yr. In how many years it will become eight times?
Options:
A) 30
B) 45
C) 50
D) 60
Show Answer
Answer:
Correct Answer: B
Solution:
- Let the sum be Rs. x. Then, amount after $ 15yr=2x $
$ \Rightarrow $ $ 2x=x{{( 1+\frac{r}{100} )}^{15}} $
$ \Rightarrow $ $ 2={{( 1+\frac{r}{100} )}^{15}} $ (i) Let after n yr sum becomes eight times of itself. Again, $ 8x=x{{( 1+\frac{r}{100} )}^{n}} $ … (ii)
$ \Rightarrow $ $ 8={{( 1+\frac{r}{100} )}^{n}} $
$ \Rightarrow $ $ {{(2)}^{3}}={{( 1+\frac{r}{100} )}^{n}} $
$ \Rightarrow $ $ {{( 1+\frac{r}{100} )}^{3\times 15}}={{( 1+\frac{r}{100} )}^{n}} $
$ \therefore $ $ n=45,yr $
BETA
