Question

The ten's digit of a 2 digit number is 5 more than the unit digit. When reversed and added to the original number the answer is 99. Find the original number?

Answer 1

Let the no. be xy
Where x=5+y,and
xy
+yx
=99
Then, y+x=9
5+y+y=9
2y=9-5
y=4/2=2
If y =2 then,
X=y+5=2+5=7
72+27=99
So x=7, y=2
Answer is 72

Answer 2

let us take the ones place digit of first no. as x
so the tenes place digit would be =5+x
so first no would be =10(5+x) +1(x)
=50+10x+x
=50 +11x


after reversing,
once place digit =5+x
tenes place digit =x
2 nd no.would be 11x +5
atq,
11x+5+11x+50=99
22x+55=99
22x=44
x=2

so original no would be
50 +11x
50 +11(2)
50+22
72
answer is 72