Question

a number consists of two digits whose sum is 9.if 27 is subtracted from the number it's digits are reversed.find the number

Answer 1

Let the digits x and y
Number 10x+y
A. T. Q
x+y=9_______1
10x+y-27 = 10y+x
x-y= 3 ________2
From 1&2,
x=6
Put x in EQ. 1
y= 3
Number = 10×6+3
= 63

Answer 2

Let the digit at ones place be x
Let the digit at tens place be y
Original number =10y+x
Reversed No
The digit at ones place will be y
The digit at tens place will be x
=> reversed no = 10x+y

A.T.Q
1) x+y = 9. ———1
2) 10y+x-27= 10x+y
=> 10y+x-(10x+y) = 27
=> 10y+x-10x-y =27
=> 9y-9x 27
=> 9(y-x) =27
=> y-x=27/9
=> y-x= 3. ————-2

Adding 1 and 2
x+y+y-x =9+3
=>2y=12
=> y=12/2
=>y=6

Putting y in 2
6-x=3
=>-x=3-6
=>-x=-3
=>x=3

Therefore the number is 63