Today America celebrates Memorial Day, the day we honor all the soldiers who protect our country. As we do for many celebrations, we spend the day eating. Memorial Day kicks off barbecuing season. It’s the dads’ big chance to prove they can cook something, and to pretend they set the food on fire on purpose. But running the grill is a lot of pressure. Not all foods cook for the same amount of time, nor do they take up the same amount of space on the rack. Plus some people want their burger “rare” (lightly cooked) or really “well done” (cooked to a crisp). It’s a giant, flame-throwing juggling act, so the chef had better know how to count.
Wee ones: If you’re grilling burgers, hot dogs, fish, and corn on the cob, how many kinds of food are you cooking?
Little kids: If the griller needs to cook 3 hot dogs, 1 steak and 5 ears of corn, how many items need to fit on the grill? Bonus: If the grill can hold 12 hot dogs, but 3 of them fall through the rack and 1 rolls off onto the ground, how many hot dogs are left?
Big kids: If the griller cooks 2 burgers the 1st round, then 3 hot dogs the 2nd round, then 2 burgers to repeat, then 3 hot dogs…how many items have been cooked by the end of the 6th round? Bonus: Which will take longer to cook, 4 rounds of burgers that take 7 minutes each, or 9 rounds of hot dogs that take just 3 minutes each?
The sky’s the limit: If the grill can hold 10 hot dogs or 5 burgers, and hot dogs take 5 minutes and burgers take 8 minutes…what’s the fastest you can cook 12 hot dogs and 6 burgers? (Assume any chunk of space can hold either 2 dogs or 1 burger…and you’ll probably want pencil and paper for this one!)
Wee ones: 4 foods.
Little kids: 9 items. Bonus: 8 hot dogs.
Big kids: 15 items, since each pair of burger and hot dog rounds covers 5 items. Bonus: The burgers take just a little longer: 28 minutes compared to 27 minutes.
The sky’s the limit: The fastest we could get is 16 minutes, by cooking 4 hot dogs (2 burger spaces) at the same time as 3 burgers (3 burger spaces). The 12 hot dogs cook in 3 rounds, taking 15 minutes; at the same time, the 6 burgers cook in 2 rounds, which take 16 minutes; then everything is done. Note that cooking all the hot dogs before all the burgers takes longer. You cook the first 10 dogs, then 2 final dogs with the first 4 burgers…but when those last 2 dogs finish, you can replace them with only 1 more burger. The 6th burger has to wait until the first 4 burgers finish. That means a 3rd round of burger-cooking, making 5 minutes plus 2 sets of 8 minutes. If you find an even faster time, let us know!
Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking before she could walk, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.