A certain sum of money invested at compound interest becomes 1.44 times of itself in 2 years. If twi

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6.Interest

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A certain sum of money invested at compound interest becomes $1.44$ times of itself in $2$ years. If twice this sum were lent at simple interest, in how many years would it double itself?

A

$2$

B

$2.5$

C

$3$

D

$5$

Solution

Let the principal (sum of money) be Rs. 100

$\Rightarrow$ Amount after 2 years $=$ Rs. 144

$\Rightarrow 100\left[\left(1+\frac{ R }{100}\right)^{2}\right]=144 \Rightarrow\left(1+\frac{ R }{100}\right)^{2}=\frac{144}{100}$

$\Rightarrow 1+\frac{ R }{100}=\frac{12}{10} ; R =20 \%$

Now, we have to make amount from Rs. 200 to Rs. $400 .$ So, SI would be Rs. 200 .

$\Rightarrow 200=\frac{200 \times 20 \times T}{100} \Rightarrow T=5$ years

Standard 13

Quantitative Aptitude

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