Question

A number has two digits. the digit at ten's place is four times the digit at unit place. if 54 is subtracted from the number, the digits become reserved. find the number.

Answer 1

82 is the right answer

Answer 2

${\pink{\underline{\textsf{\textbf{Answer : }}}}}$

The number is 82.

${\purple{\underline{\textsf{\textbf{Explaination : }}}}}$

Let's assume

➩ The numbers are x(ten's digit) and y (ones digit)

Number formed :

➩ 10x + y

Reversing the digits :

➩ 10y + x

As it is told that x is 4 times y

So, x = 4y ...... (i)

According to the question,

$\sf : \implies \: (10x + y) - (10y + x) = 54 \\ \sf : \implies \: 10x + y - 10y - x = 54 \\ \sf : \implies \: 9x - 9y = 54 \\ \sf : \implies \:9( x - y) = 54 \\ \sf : \implies \: x - y = \frac{54}{9} \\ \sf : \implies \: x - y = 6 \\ { \underbrace{ \textbf{ \textsf{ From ..(i)}}}} \\ \sf : \implies \: 4y - y = 6 \\ \sf : \implies \: 3y = 6 \\ \sf : \implies \: y = \frac{6}{3} \\ \sf : \implies \: y = 2$

After solving we get :

➩ y = 2

And also,

x = 4y

x = 4*2

x = 8

Hence,

The number is :

➩ 10x + y

➩ (10*8) + (2)

➩ 80 + 2

➩ 82 ans.