Question

A two digit number is such that the sum of its digits is 4. If 18 is added to the number, it's digits are reversed. Find the number.

Answer 1

let the number on one's position be y
number on hundred's position be x
we know 2 digit number be of form the form 10x+y
given sum of number is 4
'that is
x+y=4-------1

when 18 is added ,digit get reversed
so 10x+y+18=10y+x (reverse of two digit nummber is 10x +y is 10y+x)
9x-9y=-18
x-y=-2(dividing by 2)------2

adding eqn 1 and eqn2
2x=2
x=1
sustitute in eqn1
1+y=4
y=3
so the number is
10x+y
=10(1)+3
=13