Question 12 Marks
A certain sum amounts to $Rs. 5,292$ in two years and $Rs. 5,556.60$ in three years$,$ interest being compounded annually. Find$: $the original sum.
Answer
View full question & answer→Let the sum of money $ = Rs. 100$
Interest on it for $1^{\text {st }}$ year $=5 \%$ of $Rs. $$100=$$Rs. 5$
$\Rightarrow$ Amount in one year$= Rs.$$100+Rs.$ $5=$$Rs. 105$
Similarly$,$ amount in two years $=$ $Rs.105+5 \%$ of $Rs. 105$
$=$ $Rs. 105+ Rs. 5.25$=$Rs. 110.25$
When amount in two years is $Rs. 110.25 , \sum = Rs. 100$
$\Rightarrow$ When amount in two years is $Rs. 5,292,$
$\text { sum }=\text { Rs. } \frac{100 \times 5,292}{110.25}=\text { Rs. } 4,800 \text {. }$
Interest on it for $1^{\text {st }}$ year $=5 \%$ of $Rs. $$100=$$Rs. 5$
$\Rightarrow$ Amount in one year$= Rs.$$100+Rs.$ $5=$$Rs. 105$
Similarly$,$ amount in two years $=$ $Rs.105+5 \%$ of $Rs. 105$
$=$ $Rs. 105+ Rs. 5.25$=$Rs. 110.25$
When amount in two years is $Rs. 110.25 , \sum = Rs. 100$
$\Rightarrow$ When amount in two years is $Rs. 5,292,$
$\text { sum }=\text { Rs. } \frac{100 \times 5,292}{110.25}=\text { Rs. } 4,800 \text {. }$