Zero a multiple of 5???

[marcflores]

My wife, who is great at math and did well for herself at Harvey Mudd, missed a question on a practice GMAT. At the answer section it said, "Remember, zero is also a multiple of 5."

Is this correct? Zero, I thought, was not a multiple of anything!

[morphism]

If we use the definition that an integer a is a multiple of an integer b if there is an integer c such that a=b*c, then zero is a multiple of 5 because 0=0*5. In fact, zero is a multiple of any integer.

On the other hand, the only thing that is a multiple of zero is zero itself.

[marcflores]

That is true. Thanks for clarifying that.