Today From Bedtime Math: All You Can Eat (for Real)

How many pounds of your favorite foods do you eat in a year? In ten years? Count up the yummy moments in this tasty Bedtime Math problem!
By Laura Overdeck
Aug 25, 2015

Ages

3-13


Aug 25, 2015

Have you ever wondered how much food you eat in a day? How about the amount you eat in your whole life? In his book Numberland, Mitchell Symons guesses that we each eat 35 tons of food. Does that make sense? How many pounds of food do you think you eat every day? Well, it must be a pretty big number: scientists have figured out that on average we each take in about 150 hamburgers a year, 20 gallons of milk (about 160 pounds), and almost 3 dozen donuts. It all adds up, but to what? If you eat about 1 pound of food a day, that's about 400 pounds a year, or 1 ton every 5 years. As we see, Mitchell thinks it's more than that — but is he right?

Now see if you and your kids can come up with the answers to these math challenges:

Wee ones: If you eat 2 pounds of apple pie on Saturday and 1 pound on Sunday, how much do you eat in total that weekend?

Little kids: If you eat 2 pounds of food a day, how much do you eat in 1 week?  Bonus: If 1/2 of that is spaghetti, how many pounds of spaghetti did you pound down?

Big kids: If you eat 10 pounds of food a week — a little more than a pound a day – how much would that be in 1 year? (Hint if needed: You can count a year as 52 weeks.)   Bonus: If half of that was your favorite food — say, ice cream — how many pounds of your favorite food do you eat?

The sky's the limit: If you eat just 1 ounce of food the 1st day, 2 ounces the 2nd day, and so on, on what day will you have eaten 5 pounds in total? (Reminder: A pound has 16 ounces.)
 
Answers:
Wee ones: 3 pounds.
Little kids: 14 pounds.  Bonus: 7 pounds.
Big kids: 520 pounds.  Bonus: 260 pounds of ice cream.
The sky's the limit: 5 pounds comes to 80 ounces. Adding 1+2+3…etc. gives you the triangle numbers, where things can be stacked in growing rows to make a triangle. If you just do trial and error, you'll get 10 ounces total on day 4, then 15, 21, 28, 36, 45, 55, 66, 78…so on the 13th day you'll reach the 80th ounce. The shortcut: a triangle with n as the biggest number added will have a total of n x (n+1)/2, so on the 12th day you'll have 12 x 13 divided by 2, or 78 ounces.
 

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