Bhuvi wrote:

which of the following CANNOT be the greatest common divisor of two positive integers x and y ?

A 1

B x

C y

D x-y

E x+y

Do you assume a random value of x and y for this ?

Thats E: (x +y). Greatest common divisor (GCD) of two integers can never be the sum of these integers. For example:

1 and 1 cannot have GCD of 2.

1 and 5 cannot have GCD of 6.

2 and 3 cannot have GCD of 5.

2 and 5 cannot have GCD of 7.

5 and 5 cannot have GCD of 10.

15 and 25 cannot have GCD of 40.

Similarly, x and y cannot have GCD of (x+y).

However (x-y) is possible: Suppose x = 4 and y = 6. The GDC is x-y = 6-4= 2.

1, x, and y can easily be the GCD of integers x and y.

atish wrote:

hariharakarthi wrote:

Ans E.

GCF of x and y can't be greater than the difference between x and y.

Are you sure about that rule?

GCF of 2 equal numbers is the number itself > difference of the two numbers (0)

I would say the GCF of two numbers can't be greater than either of the numbers.

Thats correct.

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Verbal: http://gmatclub.com/forum/new-to-the-verbal-forum-please-read-this-first-77546.html

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Gmat: http://gmatclub.com/forum/everything-you-need-to-prepare-for-the-gmat-revised-77983.html

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