This Week From Bedtime Math: Penny Pincher
What is Bedtime Math? A message from Laura: Bedtime Math is a pretty simple idea: We all know we should read to our kids at night, but what about math? My husband and I have done fun, mischief-loaded math problems with our kids at night for years, and when at age 2 our third child started hollering for his own math problem, we realized we were onto something: In a world where so many people say, "Ewww, math!" we had created a household culture where kids don't just tolerate math, they actually seek it out. Now, every week, we'll be posting a new problem right here on Scholastic Parents!
Have you ever visited a tourist spot — a special place where lots of people come to visit — and seen one of these machines? It's called a penny press or penny pincher. It takes your penny and rolls it between heavy metal wheels that squash it flat, stamping a picture of that special place on it. You stick the penny and a few coins into the slots, push them in, and then choose your design. As you turn the crank and the gears squash your penny, it gets molded into that design — this picture shows one from the Alamo in Texas. Penny pressing usually costs a few quarters, and you spent the penny, too…so you won't be able to buy anything with that pointy copper oval after that. But, you won't want to give it up as a souvenir, anyway.
Now that your mental gears are turning, try challenging your kids with these math challenges:
Wee ones: If you have to put 3 quarters into the machine with your penny, how many coins do you need in order to penny-pinch?
Little kids: If the penny pincher needs just 1 quarter and your penny, how many cents does it gobble up to start? Bonus: If you have 3 dimes in total and you trade them for a quarter and a bunch of pennies, how many extra cents will you have left after pressing your penny? (Reminder: a quarter equals 25 cents.)
Big kids: If the penny pincher wants 61 cents in total, what's the fewest number of coins it needs to do the project? (Other reminders: a nickel is 5 cents and a dime is 10 cents. Assume a quarter is the largest coin it takes.) Bonus: If, like most presses, the machine wants 3 quarters, how many pennies does it need to press to earn a round number of dollars?
Wee ones: 4 coins in total.
Little kids: 26 cents. Bonus: 4 coins left, since you'll need 26 of your 30 cents.
Big kids: 4 coins: 2 quarters, a dime, and the penny. Bonus: It needs to press 4 pennies (what's with all the 4′s today?) as that will earn it $3.00.