xy is a 2 digit integer whose reverse, yx, is x less than twice xy. What is the sum of x and y?
A) 8
B) 9
C) 11
D) 12
E) 13
The OA is E.
What formula solves this PS question? I couldn't establish it.
xy is a 2 digit integer whose reverse. . .
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The 2-digit number [xy] can be represented as 10x + y, thus, its reverse [yx] = 10y + xVincen wrote:xy is a 2 digit integer whose reverse, yx, is x less than twice xy. What is the sum of x and y?
A) 8
B) 9
C) 11
D) 12
E) 13
The OA is E.
What formula solves this PS question? I couldn't establish it.
We are given that [yx] = 2*[xy] - x
10y + x = 2(10x + y) - x
4y = 9x
Since 4 and 9 are co-prime, and x and y are single-digit numbers, only possible values of x = 4 and y = 9.
Thus, the sum of the digits = 4 + 9 = 13.
The correct answer: E
Hope this helps!
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