Question

At what rate of interest per annum will a sum becomes $5$ times in $20$ years at S.I.?

• A. $10\%$
• B. $16\%$
• C. $20\%$
• D. $25\%$

Answer 1

Answer: (C)

$20\%$

Interest earned $=P\times r\times t$

$P=$ Principal amount

$r=$ Rate of interest

$t=$ Time period

Here, sum becomes $5$ times in $20$ years,

$\Rightarrow$ Interest earned $4$ times the principal amount.

$\therefore 4P=P\times r\times 20$

$r=\frac{4}{20}\times 100=20\%$