Question

The sum of the digits of a two-digit number is 9 less then the number. Which of the following digits is at unit's place of the number ?

• A. 1
• B. 2
• C. 4
• D. Data inadequate

Answer 1

The correct option is A 1

Let $x,y$ are the digits of a number. Then the number $=10x+y$

as per condition : $10x+y-9=x+y$

Then as per the given problem,

$x+y=10x+y-9$

or, $9x=9$

or, $x=1$

So, we can say that for any value of y from 1 to 9, the condition satisfies.

for eg: if the number is 18

18–9 = 1+8

9=9 , satisfied.

So the tenth's place digit is $1$.