| A sum of Rs. 12000 deposited at compound interest becomes double after 5 yr. After 20 yr, it will become [SSC (CGL) 2011] |
A) Rs. 48000
B) Rs. 96000
C) Rs. 190000
D) Rs. 192000
Correct Answer: D
Solution :
| Given, P=12000, then |
| \[A=P{{\left( 1+\frac{r}{100} \right)}^{t}}\] |
| \[\Rightarrow \]\[\frac{A}{P}={{\left( 1+\frac{r}{100} \right)}^{t}}\]\[\Rightarrow \]\[2={{\left( 1+\frac{r}{100} \right)}^{5}}\] |
| On squaring twice both sides, we get |
| \[{{2}^{4}}={{\left( 1+\frac{r}{100} \right)}^{20}}\]\[\Rightarrow \]\[16={{\left( 1+\frac{r}{100} \right)}^{20}}\] |
| Hence, the principal will become 16 times, i.e. |
| \[\text{Rs}\text{. (16}\times \text{12000)= Rs}\text{. 192000}\] |
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