Question

A boy Aru was asked to multiple a number by 12.by mistake he multipled 21 and got his answer 63 more than the correct answer. The number was

Answer 1

Let the number be x .

Then the correct answer :-

$\texttt{= \: 12 × \: } x$

$=\texttt{ 12}x$

So, the correct answer = 12x

Aru multiplied the number by 21 :-

$= \texttt{21 \: × \: } x$

$= \texttt{21}x$

So, Aru's answer after multiplying the number with 21 = 21x

His final result :-

= 63 more than the correct answer

$= \texttt{12}x \texttt{ \: + \: 63}$

These expressions can be combined and written in an equation as :-

$\hookrightarrow \: \texttt{21}x \texttt{ \: = 12}x \texttt{ \: + 63}$

Let us solve this equation to find the number :-

$=\texttt{ 21}x \texttt{ \: = 12}x \texttt{ \: + 63}$

$=\texttt{ 21}x \texttt{ \: - \: }\texttt{12}x\texttt{ \: = \: 63}$

$=\texttt{9}x \texttt{ \: = \: 63}$

$= x\texttt{ = } \frac{\texttt{63}}{\texttt{9} }$

$=\color{hotpink} x \texttt{ \: = \: 7}$

So, the value of the number = 7

Let us check whether or not we have found out the correct number by placing 7 in the place of x :-

$=\texttt{ 21 \: × \: 7 = 12 \: × \: 7 \: + \: 63}$

$= \texttt{147 \: = \: 84 \: + \: 63}$

$=\texttt{ 147 = 147}$

$= \texttt{\color{olive}LHS =\color{hotpink} RHS }$

As the left hand side of the equation is equivalent to the right hand side of the equation we can conclude that we have found out the correct value of the number .

Therefore, the number was = 7

Answer 2

Hope this helps.......