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

The answer is provided as a whole explanation

Step-by-step explanation:

Regrouping is the presentation of a number or decimal with its number groups. For example, we can represent 0.25 in this way:

0.25 = 0.2 + 0.05

0.25 = 2 tenth + 5 hundredth  

We can also write 0.25 as:

0.25 = 0.1 + 0.15

0.25 = 1 tenth + 15 hundredth

Regrouping is handy to simplify a mathematical calculation since we know how many tenth or hundredth we have got in this case.