Carcass wrote:
In the correctly-worked addition of the two-digit numbers below, each letter represents a different positive integer less than 10. Which of the following could represent the number \(1SK\)?
\(XY+\)
\(YY\)
-------
\(1SK\)vf
I. 178
II. 134
III. 120
(A) I only
(B) II only
(C) III only
(D) I and II
(E) I, II, and III
XY can be written as 10X + Y
YY can be wtitten as 10Y + Y
Sum (1SK) = 10X + 12Y
Let's check the option choices;
I. 178 = 10X + 12YX = 9, Y = \(\frac{88}{12}\) - NO
X = 8, Y = \(\frac{98}{12}\) - NO
X = 7, Y = 9 - YESII. 134 = 10X + 12YX = 9, Y = \(\frac{44}{12}\) - NO
X = 8, Y = \(\frac{54}{12}\) - NO
X = 7, Y = \(\frac{64}{12}\) - NO
X = 6, Y = \(\frac{74}{12}\) - NO
X = 5, Y = 7 - YESIII. 120 = 10X + 12YX = 9, Y = \(\frac{30}{12}\) - NO
X = 8, Y = \(\frac{40}{12}\) - NO
X = 7, Y = \(\frac{50}{12}\) - NO
X = 6, Y = 5 - YESHence, option E