The post “Star Wars” Star Drives Your Car appeared first on Bedtime Math.

]]>Robots come in all kinds of shapes. Some are boxy, some are round. One of the world’s favorite robots is little BB-8 from the *Star Wars* movies. He’s just a white and orange ball that rolls and makes cute beeping sounds. Maybe that’s why he’s so cute. Well, our friend and fan Caitlyn R. sent us a great photo and video of a car with a wheel that looks just like BB-8. BB-8’s head is painted right above the tire, so as the wheels turn, it looks like BB-8 is holding up the car! We could paint a lot of fun, round objects on car wheels. Cookies, donuts, a Ferris wheel…let’s see what drives best.

*Wee ones:* What shape is a car tire?

*Little kids:* If that car’s 1 wheel looks like BB-8 and the rest are plain, how many plain wheels does the car have? *Bonus:* If you have 2 cars and paint all the left-side wheels to look like chocolate chip cookies, how many cookie wheels are there?

*Big kids:* If the car has 1 BB-8 wheel, and another wheel that looks like a donut with sprinkles, how many different ways can you place the BB-8 wheel and donut wheel on the car? *Bonus:* If the BB-8 rolls that car 100 feet per minute, how far can he drive the car in 30 minutes?

*The sky’s the limit:* If you have a fleet of 20 cars, and of all their wheels, there are twice as many donut wheels as BB-8 wheels, and the same number of cookie wheels as donut wheels, what’s the greatest number of BB-8s there can be?

Answers:

*Wee ones:* A circle, from the side. In 3D it’s an “annulus” (ring shape).

*Little kids:* 3 plain wheels. *Bonus:* 4 cookie wheels.

*Big kids:* 12 ways: for each of the 4 spots for the BB-8 wheel, there are 3 different spots the donut wheel can go. *Bonus:* 3,000 feet (more than 1/2 mile).

*The sky’s the limit:* 16 BB-8 wheels. If there’s 1 set of BB-8s, then there are 2 sets of just as many donuts and cookies, making 5 equal-sized sets in total. There are 80 wheels in total — remember, each of those 20 cars has 4 wheels! — and 1/5 of 80 is 16. So that’s how many wheels make up the BB-8 set, and there are 32 donuts and 32 cookies.

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]]>The post How Many Years in a Hamster Year? appeared first on Bedtime Math.

]]>What do people mean by “dog years”? Every animal has some number of years it’s expected to live. We people live for about 78 years, but dogs live a much shorter life, about 1/7 of ours. So each year for us feels like 7 years to them. Then our friends Victoria and Emilia I. asked, can you measure years using other animals? And Sophie L. asked how old her cats are in cat years. Well, let’s see how many times an animal’s life divides into one “people-life,” and that’s how long 1 year feels to them. If cats live 10 years, then they can fit about 8 cat lives into a human lifetime, so each “cat year” is 8 years. A 6-year-old cat feels 48 years old! Hamsters live about 3 years, so 1 year for us is 26 hamster years. That sounds like one busy year.

*Wee ones:* If a “cat year” is 8 years and a “rabbit year” is 1 year longer, how long is a rabbit year?

*Little kids:* If guinea pigs live about 6 years and cats live about 10 years, for which one does a real year feel longer? *Bonus:* If your dog has been chewing on your family’s shoes for 2 years, how long is that in dog years? (*Reminder if needed:* A year for us feels 7 times as long to a dog).

*Big kids:* Some say that the first 2 years of a dog’s life each feel like 10 years to them, then each year after that feels like 4. If a dog has lived 5 real years, now how long is that in dog years? *Bonus:* If goldfish live about 2 years, how long does 1 of our years feel to them, if we live to 78?

Answers:

*Wee ones:* 9 years.

*Little kids:* For the guinea pig, since it’s a bigger fraction (piece) of his life. *Bonus:* 14 years.

*Big kids:* 32 years, since it feels like 10+10+4+4+4. *Bonus:* 39 years.

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]]>The post A Day for Our Friend Earth appeared first on Bedtime Math.

]]>Today is Earth Day, that day when we think about this amazing, beautiful planet that we call home, and how we can take better care of her. Earth Day started back in 1970 to remind us to think about the environment. But we should think that way every day, right? Americans alone make about 1,600 pounds of trash *per person* per year – that’s over 500 billion pounds. And the plastic in that garbage will take 100 to 400 years to break down in a landfill to become dirt. So we have to do things differently. Not only does recycling save space in those garbage dumps, but it also takes less energy to make a bottle from used glass or plastic than from new stuff. The energy saved by recycling one plastic bottle could run your computer for 25 minutes. And a 3-foot stack of recycled newspaper saves one whole tree! So let’s celebrate Earth Day every day.

*Wee ones:* If you get really good about recycling paper, plastic, glass and aluminum, how many different materials are you recycling?

*Little kids:* Recycling a 3-foot stack of newspaper saves 1 tree. If you want to save 3 trees, how tall a pile do you need to recycle? *Bonus:* The energy saved by recycling 1 plastic bottle could run a computer for 25 minutes – but a recycled glass bottle could run it 5 minutes longer. How long is that? Count up if it helps!

*Big kids:* The U.S. prints 4 million tons of junk mail every year – mail we don’t even want. At 2,000 pounds per ton, how many pounds of paper is that? (*Hint:* You can break this into multiplying by 1000 and then by 2.) *Bonus:* Americans throw out 2.5 million plastic bottles every hour. If we saved just half a million bottles each hour, how many would we save in a 24-hour day?

Answers:

*Wee ones:* 4 different materials.

*Little kids:* 9 feet of paper. *Bonus:* 30 minutes.

*Big kids:* 8 billion pounds. *Bonus:* 12 million bottles.

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]]>The post Crickets Who Count appeared first on Bedtime Math.

]]>We humans aren’t the only creatures who can do math. Some of our six-legged friends are just as good with numbers. As the weather gets warmer you might hear crickets chirp, which they do by rubbing their legs together (the boy crickets, at least). The warmer the weather, the faster they chirp. Here’s the kicker: you can use their speed of chirping to figure out the temperature! The temperature is a number in degrees that tells you how hot something is, and the higher the number, the hotter. For a rough guess, count the number of chirps in 14 seconds, then add 40. That will tell you the outside temperature in degrees Fahrenheit. Try it out and amaze your family and friends!

*Wee ones:* If you’re counting cricket chirps, what number do you say right before the 7th chirp?

*Little kids:* A cricket has 6 legs, like any insect. If he’s rubbing 2 legs together to chirp, how many legs does he have left to stand on? *Bonus:* If you’ve been counting for 9 seconds, how many seconds until you have your full 14 seconds of chirps?

*Big kids:* If you count 20 chirps in that magical 14 seconds, what’s the outside temperature in Fahrenheit? (*Reminder if needed:* You count the chirps, then add 40.) *Bonus:* If a cricket chirps 3 times per second, is it warm enough out to melt a chocolate bar, which melts at 88 degrees?

*The sky’s the limit:* Who’s chirping faster, a cricket who chirps 12 times in 15 seconds, or a cricket who chirps 36 times in a minute?

Answers:

*Wee ones:* 6.

*Little kids:* 4 legs. *Bonus:* 5 more seconds.

*Big kids:* 60 degrees Fahrenheit. *Bonus: *No, because 3 times per second for 14 seconds is 42, plus 40 gives you only 82 degrees.

*The sky’s the limit:* The first cricket. 36 chirps in 60 seconds is the same as 9 chirps in 1/4 of a minute, or 15 seconds. The first cricket chirps 12 chirps in that same time.

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]]>The post Dance Like a Cockatoo appeared first on Bedtime Math.

]]>We know we can teach an animal to dance: we see it at the circus all the time. But do regular wild animals hear music and dance on their own, matching the beat? One scientist watched thousands of YouTube videos of animals “dancing” to music, and found 33 of them were in fact dancing. Of those 33 animals, 29 of them were birds! (The rest were elephants.) Another scientist tested one cockatoo named Snowball, playing the bird’s favorite song, “Everybody” by the Backstreet Boys.Whether he sped up the song or slowed it down, Snowball bopped to the beat about 1/4 of the time. There’s almost no chance that happened by accident, so that bird really can boogey.

*Wee ones:* If you clap to the beat 4 times, what numbers do you say?

*Little kids:* If the 5th dancing bird and the next 2 after that all liked rap music, what numbers were those next 2 birds? *Bonus:* If the 29 birds plus Snowball could all dance, how many dancing birds is that?

*Big kids:* If Snowball dances on the beat for 30 seconds and that’s just 1/4 of the song, how long is the song? *Bonus:* If the song “Everybody” is 3 minutes 44 seconds long, how many seconds would Snowball get to dance if she danced the whole song?

*The sky’s the limit:* If a bunch of birds and elephants hit the dance floor, and there are 4 more birds than elephants and 10 more elephant feet than bird feet, how many dancing feet are there in all?

Answers:

*Wee ones:* 1, 2, 3, 4.

*Little kids:* The 6th and 7th birds. *Bonus:* 30 birds.

*Big kids:* 120 seconds, or 2 minutes. *Bonus:* 224 seconds.

*The sky’s the limit:* 62 feet. If we have b birds and e elephants, then we have 2b bird feet and 4e elephant feet. Using those:

b = e + 4 , so 2b = 2e + 8

4e = 2b + 10

Substituting the first equation into the second, we get

4e = 2e + 8 + 10

So 2e = 18, and e = 9. There are therefore 9 elephants and 13 birds, giving us 36 elephant feet and 26 bird feet (which is 10 fewer than the elephant feet, like it’s supposed to be). That gives us 62 dancing feet in total.

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]]>The post Nelly’s Nose appeared first on Bedtime Math.

]]>Dogs love people, and are happy to play just about any game with us. Usually they like to catch, fetch, or just chase us across the yard. But here’s a dog who likes a different game: balancing things on her head. Nelly’s owners can give her just about anything — a toy plane, a light bulb, a carton of eggs — and she can hold it on her nose with no problem. Her owners have taken lots of pictures of her in these poses, and now Nelly’s nose is famous. Dogs also like to snack, but Nelly can balance a stack of potato chips on her nose, a grapefruit section, and a long loaf of bread without eating them. Nelly is a golden retriever, a breed (type) of dog that loves to fetch things. In Nelly’s case, looks like the owners are doing all the fetching!

*Wee ones:* If you can balance a flowerpot on your head for 4 seconds and Nelly can hold it for 6 seconds, whose falls first?

*Little kids:* If Nelly balances a blender for 5 seconds and a pint of ice cream for 7 seconds, how much longer did she balance the ice cream? Count up from 5 if it helps! *Bonus:* If she balances one right after the other, how long does the whole stunt take?

*Big kids:* If Nelly balances 2 stuffed animals, then 3 Lego cars, then 2 stuffed animals to repeat, what kind of toy is the 25th one she balances? *Bonus:* Of her first 50 toys in this pattern, how many would be stuffed animals?

*The sky’s the limit:* If we ask Nelly to balance a pineapple, a lamp, a juicebox, and a stack of toilet paper rolls in any order she wants, in how many orders can she balance them if the pineapple is always 3rd? (*Hint if needed:* What if the pineapple were always 1^{st}?)

Answers:

*Wee ones:* Your flowerpot.

*Little kids:* 2 seconds longer. *Bonus:* 12 seconds.

*Big kids:* A Lego car, because every set of 5 ends in a Lego car. *Bonus:* 20, since 2 out of every 5 are stuffed animals.

*The sky’s the limit:* Just 6 ways. Having the pineapple third is the same as always having it 1^{st}, so you can ignore it and find the different orders for the other 3 objects. You have 3 choices for the 1^{st} of those slots (L, J or T), and you have 2 choices for each of those choices, giving you 3 x 2; then you have just 1 item left, so it’s 3 x 2 x 1 = 6. If you want to write out the orders, they are LJT, LTJ, JLT, JTL, TLJ, TJL…and you can stick in a P in the 3^{rd} slot to see the real results.

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]]>The post How to Be a Juggler! appeared first on Bedtime Math.

]]>It’s International Juggler’s Day, a day all about the amazing act of juggling. It’s hard enough to catch a ball with one hand. But to toss a whole bunch of them into the air and catch them over and over with your 2 hands — that’s something else! There are two basic ways to juggle: throwing the balls, bananas or bean bags up and around in a circle, or throwing them across each other in an X. The more things in the air, the harder it is. The world record for the most balls juggled is 11, set by Alex Barron in 2012. He made 23 catches in a row! Meanwhile, the record for juggling flaming torches is 7, held by Anthony Gatto back in 1989. He also once juggled 3 running chainsaws, and made 94 catches in a row. The rest of us are better off practicing with bananas.

*Wee ones:* If you toss a banana, then a rubber chicken, then a banana again, then a rubber chicken…what do you juggle next?

*Little kids:* It’s easier to juggle odd numbers of things than even numbers. If you have 6 bananas, what are the 2 closest odd numbers? *Bonus:* If you have 8 flaming torches and your friends each want to practice with just 3, how many friends can you give 3 torches, and how many are left over?

*Big kids:* If Alex juggled 11 balls and made 23 catches, with the balls caught in the same repeating order, how many balls were caught more than twice? *Bonus:* If each ball weighed 6 ounces, how many pounds of balls was he throwing? (Reminder if needed: A pound has 16 ounces).

Answers:

*Wee ones:* A banana.

*Little kids:* 5 and 7. *Bonus:* 2 friends, with 2 torches left over, since you can give away 6 at most.

*Big kids:* Just 1, since the 11 balls went through 2 catches each to make the first 22 catches. *Bonus:* 4 pounds 2 ounces. They weigh 66 ounces total, and 64 ounces is the biggest multiple of 16 that’s still less than that.

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]]>The post Top 10 Pets appeared first on Bedtime Math.

]]>Lots of animals can make great pets: dogs, cats, guinea pigs, even flamingos if you have a pond. So what are the most popular household pets? There are two ways to answer this. If you count how many houses have one kind of pet or another, there are more dog houses than anything else — dogs win! But if you count animal by animal, a house can have more than one of an animal. In that case, cats and fish win. There are 81 million cats and almost 76 million fish, but 72 million dogs. Hey, as long as you’re putting fish food in the tank, you might as well have 20 fish in there, right? Rabbits, turtles, and guinea pigs all make the list, too, along with “livestock” like chickens and sheep. Wonder if anyone has one of each!

*Wee ones:* Who has the most legs, a flamingo, a fish or a dog?

*Little kids:* If you have 2 cats, 4 hamsters and a ferret, how many whiskery noses do they have? *Bonus:* If there are 20 houses on your street and all but 1 have a pet, how many homes have pets?

*Big kids:* 9 million homes have 76 million fish all together. If 8 million homes have just 1 fish, how many millions of fish are left for the rest? *Bonus:* 43 million houses have dogs, but just 37 million have cats. If 10 million houses in that whole set have both, how many have just 1 kind of pet?

*The sky’s the limit:* Say all the neighbors on your street have pet hamsters, turtles, and penguins. If the hamsters and turtles add up to 16, the turtles and penguins add up to 10, and the hamsters and penguins add up to 8, how many of each do you have?

Answers:

*Wee ones:* The dog, which has 4 legs.

*Little kids:* 7 noses. *Bonus:* 19 houses.

*Big kids:* 68 million fish. *Bonus:* 60 million homes (33 m dog homes and 27 m cat homes).

*The sky’s the limit:* 7 hamsters, 9 turtles, and 1 penguin. If you drop from 10 total to 8 total when you change from turtles-and-penguins to hamsters-and-penguins, there must be 2 more turtles than hamsters. They add up to 16, which means if the turtles dropped by 2, they’d be equal and add to 14. So there are 7 hamsters, which gives us 9 turtles. There are 10 pets when you add penguins to turtles, so there’s just 1 penguin.

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]]>The post Who Invented Hopscotch? appeared first on Bedtime Math.

]]>Can you hop? Jumping up and down on just one leg isn’t easy. Even bunnies don’t “hop” for real: they really jump off both back feet. So hopping is the big challenge in the game hopscotch. More than 1,000 years ago, soldiers in the Roman army got exercise by hopping through numbered squares drawn on the ground. Little kids liked the game so much that they copied it. They drew their own smaller squares, and that’s where hopscotch came from! In hopscotch you can write whatever numbers you like, throw rocks to block squares, and make up your own rules. So you can invent your own new game every time.

*Wee ones:** *What shapes do you see on this hopscotch board?

*Little kids: *If you write the numbers 1 through 8 in order on your hopscotch board, what number do you write before the 6? *Bonus: *If your hopscotch board has spaces 1 through 10, how many hops do you do if you land only on the odd numbers once each?

*Big kids: *If 6 people and their 6 pet bunnies start hopping, how many feet are hopping all together?* (Remember: *bunnies hop on 2 feet, but we don’t!) *Bonus:* If you number 1 through 12, and skip all the multiples of 4 as well as the non-4-multiple square your rock landed on, how many hops do you do to hop to the end and back?

*The sky’s the limit:* If a bunch of people and bunnies play hopscotch, and there are 8 players in total but 1 more bunny foot than people feet hopping, how many bunnies are playing?

Answers:

*Wee ones:* Squares and rectangles (both are 4-sided shapes), and at the end, almost a half-circle.

*Little kids: *The 5. *Bonus: *5 hops: on the 1, 3, 5, 7, and 9.

*Big kids: *18 feet. *Bonus: *16 hops, since you do 8 in each direction. You skip 4 squares: the 4, 8, 12, and rock.

*The sky’s the limit:* 3 bunnies, who hop on 6 feet while the 5 people hop on 5. You can start with 8 people on 8 feet, and each time you swap in a bunny for a person, the bunny feet go up by 2 while the people feet go down by 1, so the gap grows by 3. The gap started at +8 for the people and you need a gap of -1, so you have to change the gap by 9. You’ll need 3 swaps to do that, so 3 bunnies.

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]]>The post Orange You Glad You’re Not Round? appeared first on Bedtime Math.

]]>It’s funny how almost all fruits are round. Apples, oranges, watermelons, kiwis…why is that? Mother Nature may have a few reasons, one being that the fruit can roll away once it falls from the tree, and spread seeds for new trees. But then what about these 5-sided oranges from Japan? Don’t worry — the oranges don’t grow on the tree like that by themselves! The farmer puts a wooden frame around each one as it hangs from the branch. As the orange grows, it squishes itself into the corners and takes that 5-sided shape. The Japanese use this same trick to grow cube-shaped watermelons and other funny-shaped fruit…and none of it will roll off your plate.

*Wee ones:* Which has more sides, a square watermelon slice (4 sides) or this orange slice (5 sides)?

*Little kids:* What do you call a shape with 5 straight sides, like we see here? *Bonus:* It took the fruit growers 3 years to make this idea work. If they got it working in 2014, when did they start?

*Big kids:* By making cube-shaped watermelon, the Japanese can fit more pounds of watermelon on a shelf. If you have 4 rows of 6 cube watermelons, how many melons do you have? *Bonus: *If you have 20 5-sided orange slices side by side to make a full circle, so each one is touching the 2 it sits between, how many orange edges aren’t touching anything?

*The sky’s the limit:* If you stack a cube of 5 watermelons across, 5 front to back and 5 tall, how many watermelons are hidden inside, with no faces facing the air or the floor?

Answers:

*Wee ones:* The 5-sided orange slice.

*Little kids:* A pentagon. *Bonus:* In 2011.

*Big kids:* 24 melons. *Bonus:* 60, since each orange has 3 free edges.

*The sky’s the limit:* 27, since that inner cube will be 3 watermelons across, 3 deep and 3 tall!

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