The most popular sandwich in America might be the peanut butter and jelly. We’ve been making these sandwiches for over 100 years — the first known recipe is from the year 1896! It’s kind of silly that you’d need a recipe for spreading peanut butter on bread, but back in the day it was trickier than that: people had to make their own peanut butter at home. Another recipe from 1901 adds jelly to the mix. Then in 1928 sliced bread was invented, and then we knew everything we needed to know to make this easy sandwich. Today the average kid eats 1,500 PB&J sandwiches before graduating from high school — so that’s some pretty sticky math.
Wee ones: If you put a piece of bread on the plate, then top it with peanut butter, then jelly, then another slice of bread, how many layers do you have?
Little kids: If you make a mega-PB&J sandwich layering bread, then PB, then jelly, then bread again to repeat, what ingredient is the 6th layer? Bonus: Which layer of the sandwich is the 3rd layer of peanut butter?
Big kids: If the peanut butter sandwich came to life in 1896 and the jelly came along in 1901, how many years later was that? Bonus: If you eat 200 PB&J sandwiches each year, and you eat 1,600 by the time you graduate at age 17, how old were you when you started?
Wee ones: 4 layers.
Little kids: Jelly. Bonus: The 8th layer, since the peanut butter is always 1 less than a multiple of 3.
Big kids: 5 year later. Bonus: Age 9, since it takes 8 years to eat 1,600 sandwiches at that rate.
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.