Question

A number consists of 2 digits whose sum is 8. If 18 is added to the number, its digits are interchanged. Find the number

Answer 1

let x be in tenths place and y be in units place

x+y=8...1

the desired no is 10x+y

18 is added to the no,its digits are interchanged

10x+y+18=10y+x......2

9x-9y=-18

x-y=-2

x+y=8 or,

x=8-y

putting the value of x in eqn ....2

(8-y)-y=-2

y=5

x=8-5

x=3

the desired no is 10x+y

10*3+5=35 is the no.