Question

At what rate of annual simple interest, sum will amount to five times in $40$ years?

• A. $5$%
• B. $25$%
• C. $50$%
• D. $10$%

Answer 1

The correct option is D $10$%

$A=5P,t=5$

$A=P+\frac{P\times r\times t}{100}$

$⟹4P=\frac{P\times r\times 40}{100}⟹r=10$

Hence, rate$=10\%$ per annum.