The last time I found myself standing next to a preschool-aged child, I reached my hand deep into my pocket, and grabbed several pennies.
I showed Connor the pennies and asked him to count them. He got to touch them and even pick them up. I then asked him, again, how many pennies he saw in my palm.
He told me: 7 pennies
It was then that I asked him to close his eyes while I secretly removed a penny.