Question

Anagha invested Rs. 25,000 at 11% p.a. and got Rs. 42,127.50 at the end. Find the period of investment using ready reckoner.

Answer 1

Given $P=Rs.25,000$, $A=Rs.42,127.50$ and $R=11\%$, we have to find time $n$. Using compound interest = $A-P$, we get $Rs.42,127.50-25,000=Rs.17,127.50$ as compound interest.
Thus, $Rs.17,127.5$ is the compound interest for $Rs.25,000$ at $11\%$.
Now, we find the compound interest for $Rs.1$. For the principal $Rs.25,000$, the compound interest is $Rs.17,\mathrm{127.5.}$
For the principal Rs. 1, the compound interest is $\frac{17,127.5}{25,000}=0.6851$.
Now, refer to the table corresponding to the column with $11\%$. Here $0.6851$ corresponds to $5$ years.
Hence, the period is $5$ years.