Question

A number consists of two digits whose sum is 8 . if 18 is added to the number its digits gets reversed find the number

Answer 1

let the number be X and Y
sum of two numbers is 18
x+y=8......(1)

two digit number 10x+y

if 18 is added to the number then the digits are reversed
then,
10x+y+18=10y+x
9x-9y= -18
x-y=-2......(2)

x=y-2

on putting the value of x in eq 1
y-2+y=8
y=5
then,
x=3
the two digit number is 35

Answer 2

let the ones digit be =8-x
tens digit =x
no formed=10x+8-x
=9x+8

on reversing,
one's digit =x
tens digit =8-x
no formed=80-10x+x
=80-9x
the original no=
9x+8+18=80-9x
9x+26=80-9x
9x+9x=80-26
18x=54
x=54/18
x=3
no=35