Question

You have a stuck of Pennies. Without counting the pennies, how can you know if there is an odd or even number of them?

Answer 1

Okay if this is for a math class my answer may not be acceptable but look at your pennies  its a 50/50 chance odd or even so it depend on how big the stack is. 

Answer 2

divide the stack into halves, if the stacks are equal, they are even.  If they aren't, they are odd.