Question

An amount of money invested trebled in 6 years. Find the rate of interest earned.

Answer 1

$\bold{given : } \\ \\ the \: amount \: becomes \: \\ \\ three \: times \: in \: 6 \: yrs \: \\ \\ \\ \\ \\ \bold{let} \\ \\ amount \: reserved ( principle )\: is \: \bold{100x \: rs \: } \\ \\ \\ \\ \bold{amount :} \\ \\ 3 \times 100x \\ \\\bold{ 300x }\\ \\ \\ \\ \\ \bold{simple \: interest : } \\ \\ amount \: - \: principle : \\ \\ 300x - 100x \\ \\\bold{ 200x }\\ \\ \\ \\ \\ \bold{simple \: interest : } \\ \\ \bold{ \frac{ p\times t\times r}{100} } \\ \\ here \\ \\ \: p \: = \: amount \: reserved \: \\ \\ t \: = \: time \: \\ \\ r \: = \: rate \: of \: interest \: \\ \\ \\ \\ 200x = \frac{100x \times 6 \times r}{100} \\ \\ 200x \times 100 = 100x \times 6 \times r \\ \\ r = \frac{200x \times 100}{100x \times 6} \\ \\ r = \: \frac{200}{6} \\ \\ \bold{r = 33.3 \: \%} \\ \\ \\ \\ \bold{rate \: of \: interest \: is \: 33.3 \: \%}$