Question

A sum of money at compound interest is doubled in 20 years. Then the number of years required to triple itself are

• A. 32 years
• B. 35 years
• C. 40 years
• D. 45 years

Answer 1

Answer: (A)

$A=P(1+r{)}^t$

Here,

$A=$ Final Amount

$P=$ Principal

$r=$ Rate of interest

$t=$ Time (years)

Given that, amount doubles in $20$ years

$\Rightarrow$ $2P=P(1+r{)}^{20}$

$\therefore (1+r)=\sqrt[20]{202}=1.035$

$r=0.035$

For amount to triple, let time be $t$

$\Rightarrow 3P=P(1.035{)}^t$

$\therefore t=32$ years