Question

The sum of the digit of a two number is 15.the number obtaines by interchanging digits exceed the given number by 9 find the origional number

Answer 1

The the digit at tens place be x
And ones place be y
No.= 10x+y
ATQ-
x+y=15 .......(1)
And, 10y+x= 10x+y+9
= 10y+x-10x-y-9
-9x+9y=9
9(-x+y=1).......(2)
Eliminating (1) and (2)
x+y=15
-x+y=1
2y=16
y=16/2
y=8......(3)
Putting (3) into (1)
x+8=15
x=15-8
x=7
Hence the no. Is 78