A Real Steal for Cereal

Here's your nightly math! Just 5 quick minutes of number fun for kids and parents at home. Read a cool fun fact, followed by math riddles at different levels so everyone can jump in. Your kids will love you for it.

A Real Steal for Cereal

February 18, 2016

A box of cereal weighs hardly anything. It’s pretty big and can fill a lot of bowls, but it’s so light you can throw it across the kitchen (not that we’re saying you should). Even lighter are those mini boxes of cereal that hold just 1 serving. So our friend and fan Henry S. wondered, how many of those mini boxes fit inside a big cereal box? This turns out to be a great question, because with those mini boxes you pay a LOT more for each bite of cereal. A big box holds 12 -14 ounces, and the mini boxes hold almost exactly 1 ounce. So the big box holds 12 to 14 of those little boxes. A big box costs around $3 or $4 — but so does the combo pack at Walmart, which holds just 8 mini boxes. On the other hand, those combo packs let you buy lots of flavors of cereal at once, and that might make breakfast exciting enough to be worth it.

Wee ones: How many faces (flat sides) does a cereal box have?

Little kids: If a combo pack has 2 mini boxes of rice Chex, 2 wheat Chex, and 2 cinnamon Chex, how many boxes does it have in total?  Bonus: If you eat a rice Chex on Tuesday, then wheat on Wednesday, then cinnamon the next day, then start over with rice, on what day do you eat the 2nd cinnamon Chex?

Big kids: Kellogg’s 30-pack of mini boxes has 8 different cereals. If the boxes are divided among the flavors as equally as possible, for how many flavors do you get an extra box?  Bonus: Amazon sells that 30-pack for a whopping $21! How many ounces of cereal could you get for that $21 if you instead bought a bunch of $3 12-ounce boxes?

The sky’s the limit: If each layer of the 30 pack has 10 boxes in 2 rows of 5, and that layer has 2 boxes of Apple Jacks, how many different ways can those 2 boxes be packed?

 

 

 

Answers:
Wee ones: 6 faces: front, back, left, right, top, bottom.

Little kids: 6 mini boxes.  Bonus: On Sunday.

Big kids: 6, since 3 each of every flavor gives you just 24 boxes.  Bonus: 84 ounces, since you’d be able to buy 7 12-ounce boxes.

The sky’s the limit: 45 ways. If the 1st box is in the 1st slot, the other box has 9 different slots where it can go, giving us 9 choices to start. Then if the 1st box is in the 2nd slot, the 2nd box has just 8 places to go; it can’t go in the 1st slot because you’ve already counted that situation. Then with the 1st box in the 3rd slot, the 2nd box has 7 places to go, and so on. You get 9+8+7+6+5+4+3+2+1, or 45 ways.

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About the Author

Laura Overdeck

Laura Overdeck

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 while still in diapers, 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.

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