The Sum of digits of a 2-digit number is 12. When the digits are reversed, the number becomes greater by eighteen. What is the difference between the digits in the number?
Answer
Correct Answer : b ) 2
Explanation :Let the number be xy
xy can be written as 10x + y (y is at unit's place and x is at ten's place)
when the digits are reversed, the number becomes yx
yx can be written as 10y + x
It is given that after reversal, the number becomes greater by 18.
So, we can write that
yx - xy = 18, or
10y + x - (10x + y) = 18
9y - 9x = 18
9(y - x) = 18
y - x = 2
Hence, the difference between the digits is 2.
Therefore, (b) is the correct answer.
This question was asked in UPSC CDS 1 2023 Elementary Mathematics Paper.
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