Thanks for your replies guys.

In this case:

True or False:

If ab Ξ 0 (mod 11) then a Ξ 0 (mod 11) or b Ξ 0 (mod 11). Explain your answer.

You would agree that the example:

If a=5.5 and b=2. Clearly ab is congruent to 0 modulo 11, but neither a or b is congruent to 0 modulo 11. Hence this is False.

This would indicate that it is also false.

I am not missing anything here am I???