Question

7. In what time will Rs 1000 amount to Rs 1331 at 10% per annum compound interest?
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Answer 1

$\huge \colorbox{cyan}{question}$

➡️In what time will Rs. 1000 become Rs. 1331 at 10% per annum compounded annually?

$\huge \colorbox{red}{answer}$

$\huge \colorbox{pink}{ |3| years}$

==》Principal = Rs. 1000;

==》 Amount = Rs. 1331;

==》Rate = 10% p.a. Let the time be n years.

Then,

==》[ 1000 (1+ (10/100))^n ] = 1331 or (11/10)^

==》n = (1331/1000) = (11/10)^3

==》n = 3 years

Answer 2

$\sf \underline{Given} : \begin{cases} \: \sf \: Principal = Rs \: 1000 \\ \sf \: </p><p> \: Rate \: = 10 \: \% \: \\ \sf \: Amount = \: Rs \: 1331\end{cases} \:$

$\sf \underline{To \: find} :$

• $\sf \: Time = ?$

$\sf \underline{Solution} : \:$

We have :

$\boxed{ \sf \: a = \: p \bigg \{1 + \frac{r}{100} { \bigg \}}^{t} }$

$\bigstar \: \sf \underline{ substitute \: all \: values} :$

$\sf : \implies \: 1330 = 1000 \bigg \{ \: 1 + \frac{10}{100} {\bigg \}}^{t} \\ \\ \sf : \implies \: \frac{1330}{1000} = \bigg \{ \: 1 + \frac{10}{100} {\bigg \}}^{t} \\ \\\sf : \implies \: { \bigg(\frac{11}{10} \bigg) } ^{3} = \bigg \{ \: \frac{11}{10} {\bigg \}}^{t} \\ \\ \sf : \implies \: \: \: \: \: \: \: \: \: t \: = \underline{3}$

$\sf \therefore \: \underline{ the \: \: time \: is \: \bold{3 \: year}} :$