This is the Kindergarten teaching experience in its essence:
A few days ago I introduced the penny and the concept of "one cent." Today it was the nickel. I gave all the kids a fake nickel, and we talked about how it was worth five cents, or five pennies. We put all 19 nickels in a long row on a low table, and then I had the kids set a stack of five fake pennies next to each nickel. We counted the nickels by five, and saw the whole collection was worth 95 cents (19 x 5). Then we counted the penny stacks in the same manner, by fives, to get 95 cents. Finally, I pushed all the nickels into a pile, and the stacks of pennies together into one big pile next to it. I concluded, "So this money is worth 95 cents, and all these pennies are also 95 cents, because there are 95 of them, and they're one cent each."
And one boy said, "But wait. How can they be worth the same if one pile is bigger?"
After choking back a sob, I decided we should go out to recess.
Outside, that same boy got knocked in the ear by another kids' elbow, and he cried out, "Ow! You intimidated my structural pump!"