An investment triples itself in 30 years on simple interest. The rate of interest per annum is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \(6 \frac{2}{3}\)%
When an investment triples, the amount is 3 times the principal, so the simple interest earned is twice the principal.
Assuming the principal to be 100:
Amount \(=300\), so the interest in 30 years \(=200\)
\(\displaystyle R=\frac{SI\times100}{P\times T}=\frac{200\times100}{100\times30}=\frac{20}{3}=6\frac{2}{3}\%\)