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6.Interest
hard
The simple interest accrued on an amount of $Rs. 20000$ at the end of $3$ years is $Rs. 7200$ . What would be the compound interest accrue on the same amount at the same rate in the same period?
A
$8342.36$
B
$8098.56$
C
$8246.16$
D
$8112.86$
Solution
$SI =\frac{ P \times R \times T }{100} \Rightarrow 7200=\frac{20000 \times R \times 3}{100} \Rightarrow R =12 \%$
Hence, $CI = P \left[\left(1+\frac{ R }{100}\right)^{3}-1\right]$
$=20000\left[\left(1+\frac{12}{100}\right)^{3}-1\right]=20000\left[\left(\frac{28}{25}\right)^{3}-1\right]$
$=20000\left[\frac{21952-15625}{15625}\right]=20000\left[\frac{6327}{15625}\right]= Rs .8098 .56$
Standard 13
Quantitative Aptitude
