Question

A certain sum of money double itself & no. of years is equal to rate of interest. Find rate of interest?

Answer 1

$A=2P,r=t$

$A=P+\left(\frac{P\times r\times t}{100}\right)$

$⟹2P=P+\left(\frac{P\times t\times t}{100}\right)⟹r^2=100⟹r=10\%$

Hence rate$=10\%$ per annum.