BTGmoderatorLU wrote: ↑Mon Apr 13, 2020 4:43 pm
Source: e-GMAT
If a and b are positive integers and their LCM is c. Which of the following cannot be the value of c?
A. a
B. b
C. a/b
D. a x b
E. a-b
The OA is
E
Let's take each option one by one.
A. a: Say a = 2 and b = 1, then c = 2 = a. The value of c can be a.
B. b: Say a = 1 and b = 2, then c = 2 = b. The value of c can be b.
C. a/b: Say a = 2 and b = 1, then c = 2 = a/b. The value of c can be a/b.
D. a x b: Say a = 2 and b = 1, then c = 2 = a x b. The value of c can be a x b.
E. a – b: This is the correct answer. Since a and b are positive integers, the LCM = c must also be positive; thus, for a – b to be the LCM, a > b. For a > b, even if b is a factor of a, the minimum value of LCM would be a.
The correct answer:
E
Hope this helps!
-Jay
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