Question

the digit at ten place of a two digit number is 2 times the digit at one place if digits are reversed the number become 18 less than the original number what is the original number

Answer 1

$20x + x = 21x$
10x+2x =12x
therefore
21x - 12x = 18
9x =18
x =18÷9
x =2
hence the original number is 42 (2×21)
and the reversed number is 24

Answer 2

let the unit digit be x
then ten digit will be 2x
so original no. will be.......

10(2X)+X=20X+X=21X
according to questions if digit reverse then...

10X+2X=12X

again according to questions

21X-12X=18

9X=18
X=18/9
X=2
so, from here we got unit digit =2

replacing in 10(2X)+X we got

10(2×2)+2
=10×4+2
=42

so, the original number is 42


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