HCU MCA 2013 Paper

Question : 23 of 75

Marks: +1, -0

The sum of two digits of a number is 15. If 9 is added to the number, then the digits get reversed. Which of the following is true about the number?

Solution:

(d) Let unit place digit be x and ten place digit be y.
Then, number will be of the form x + 10y.
According to the given condition,

\;\;\;\;\;\;\;\;\;\;\;\;

x + 10y + 9 = y +10x
⇒

\;\;\;\;\;\;\;\;\;\;\;\;\;\;

9x - 9y = 9

∴\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;

x - y = 1

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