Question

Suhail deposited a sum of Rs. $8000$ at compound interest in the bank at the rate of $18$% per annum for $3$ years. What interest will he get after the end of $3$ years?

Answer 1

We know that amount $A$ at the end of $n$ years at the rate of $R$ per annum is given by,

$A=P{(1+\frac{R}{100})}^n$

It is given that,

$P=8000$

$R=18\%$

$n=3$ years

Now, $A=P{(1+\frac{R}{100})}^n$

$\Rightarrow A=8000(1+\frac{18}{100}{)}^3$

$\Rightarrow A=8000{\left(\frac{100+18}{100}\right)}^3$

$\Rightarrow A=8000{\left(\frac{118}{100}\right)}^3$

$\Rightarrow A=8000\times \frac{118}{100}\times \frac{118}{100}\times \frac{118}{100}$

$\Rightarrow A=\frac{8\times 118\times 118\times 118}{1000}$

$\Rightarrow A=\frac{13144256}{1000}$

$\Rightarrow A=Rs.13144.256$

Therefore, the amount is $Rs.13144.25$

Now, compound interest, $C.I=A-P$

$\Rightarrow C.I=13144.25-8000$

$\Rightarrow C.I=5144.25$

Therefore, the interest is $Rs.5144.25$.