FDP question bank question, subtracting units

[pukul79]

Given that p is a positive even integer with a positive units digit, if the units digit of p3 minus the units digit of p2 is equal to 0, what is the units digit of p + 3?

The correct ans is 9, ok thats understandable. But why is it that numbers ending with 0 are ignored. example: suppose p is 10. then p^2 is 100 and p^3 is 1000. we get 0 as the units digit. whats wrong with my logic?

[michael_shaunn]

0 is an integer that is neither positive nor negative.

For ex:-to exclude all negative integers from the set of integers we say all non-negative integers rather than all positive integers.

[pukul79]

oh man, thats a mean question. :-)