We read Anno's Mysterious Multiplying Jar and learned how easily just one thing can multiply when you keep doubling it. I then asked them to suppose that I gave them just a penny for their allowance, but that I agree to double it each day... we decided to just do a week's worth of allowance and we used glass counters to count the days. I gave them bean counters to represent the pennies I was giving them. By the time we had finished our doubling for the week, Quentin couldn't count that high, so he sorted his counters by type.
James lost track trying to count the beans, so Sam suggested that they group them into groups of 10. They found out that just one penny doubled each day for a week would end up with 128 pennies by the end of the week. What would it be by the end of a month?....or a year?!