Bedtime Math

Your House, Made of Lego

Laura Overdeck — Fri, 11 Sep 2026 06:00:00 +0000

How much Lego would you need to build your own house? A company made an estimate to figure that out! A Lego brick is about 1/4 inch thick/tall, 5/8 inch wide, and 1 1/4 in long. Meanwhile, a *real* clay brick is 2 1/4 x 4 x 8 inches. So you need 9 x 6.4 x 6.4 Lego bricks for each real one, or about 367. The real question is, can we also build a working toilet?

Wee ones: A Lego brick is shaped like a box. How many faces (flat sides) does it have? Find a box and count them up!

Little kids: If you start building your bedroom wall with 2 red bricks, 2 yellow, 2 blue, 2 green and 2 white, how many bricks is that? Bonus: If you put 2 8-peg Lego bricks next to each other, how many pegs do you have in total – and how many ways can you place the 2 bricks so pegs line up? (Assume they’re the same color.)

Big kids: The square foot area of a space is the length times the width. If your bedroom is 10 feet long by 9 feet wide, how many square feet do you have? Bonus: If the two long walls in that 10-million brick house each have 1 million more bricks than each of the 2 short walls, how many bricks are in each wall?

The sky’s the limit: If your bedroom covers 20 square feet, what are all the combos of lengths and widths that it could be (using only whole numbers) — and which combo would need the most length of wall?

Answers:
Wee ones: 6 faces – remember to count the top and bottom along with the 4 side faces!

Little kids: 10 bricks. Bonus: 16 pegs. There are 5 ways to line them up: side by side in a square, end to end in a line, a T (one pointing to middle of the other), and 2 ways to make an L.

Big kids: 90 square feet. Bonus: 3 million bricks in each long wall, and 2 million in each short wall. Each long and short together use half the bricks – 5 million – and then you need 2 numbers 1 million apart that add to 5 million.

The sky’s the limit: 3 combos: 1 foot by 20 feet, 2 by 10, and 4 by 5. The 1 by 20 will need 42 feet of wall (20 + 20+ 1+ 1), while the 4 by 5 needs only 18 feet (5 + 5 + 4 + 4). The proportions of the space makes a huge difference!

When Rubber Duckies Sail the Seas

Laura Overdeck — Thu, 10 Sep 2026 06:00:58 +0000

Rubber duckies are fun in the bathtub – but how about in the ocean? In 1992 a giant load of rubber duckies fell off a ship near Hong Kong. The toys floated off every which way – and decades later started washing up on beaches all over the world. The ducks took only 4 years to reach the U.S., but about 15 years to reach England! They’re showing scientists which way ocean currents flow – while getting a good long bath.

Wee ones: Rubber duckies are usually yellow. See if you can find 4 yellow things in the room.

Little kids: If 5 ocean-floating rubber duckies bump into 1 more friend, how many duckies does the group have now? Bonus: If starting now some of the duckies float for 3 years before reaching a beach, how old will you be when they arrive?

Big kids: If 2 ducks, Squirty and Squeakles, start 500 miles apart, and each one floats 300 miles from their starting point, could they meet up? Bonus: If 28 rubber duckies start floating from Hong Kong, half of them make it to California, and then half of those make it to Mexico, how many duckies make it to Mexico?

Answers:
Wee ones: Items might include clothes, socks, pillows, or a picture on the wall.

Little kids: 6 rubber duckies. Bonus: Different for everyone…add 3 to your age today!

Big kids: Yes! Because if they swim straight at each other, they each need to travel only 250 miles. Bonus: 7 rubber duckies, since 14 make it to California.

Best Suited for Guinea Pigs

Laura Overdeck — Wed, 09 Sep 2026 06:00:40 +0000

We just love that someone made this suit for his pet guinea pig, Lucky. Armor is metal clothing that long-ago soldiers called knights used to wear while sword-fighting. But because metal is stiff and heavy, it was made into tiny chain links that can bend. That’s why it’s called “chain mail” armor. Who knows why Lucky needed chain mail, but his owner finally sold the suit online for more than $1,000!

Wee ones: If your guinea pig weighs 2 pounds and that little suit of armor weighs 3 pounds, which one weighs less?

Little kids: If you and Lucky suit up for battle, how many legs do you have together? Bonus: If you need to link together 60 loops to make the armor, what numbers do you say to count them off in 10s?

Big kids: If your Under Armour underwear costs $100, how many pairs could you buy instead of the $1,000 guinea-pig armor? Bonus: If you wear real metal armor that weighs 1/2 of what you weigh, and you and the armor weigh 75 pounds, what do you weigh?

Answers:
Wee ones: The guinea pig weighs less.

Little kids: 6 legs. Bonus: 10, 20, 30, 40, 50, 60.

Big kids: 10 pairs. Bonus: You weigh 50, and the suit weighs 25. You’re the same as 2 suits, so the 75 pounds is like 3 suits.

Big Bad Sun

Laura Overdeck — Tue, 08 Sep 2026 06:00:41 +0000

In the big blue sky, the Sun looks like a small, shiny circle. But the Sun is actually really huge – 100 times as wide as Earth. So our friend Evy H. asked, how much does the Sun weigh? Well, “weight” means how much Earth’s gravity pulls down on a thing. But its “mass,” or the amount of stuff in it, is 2 nonillion kilograms, which is a 2 followed by thirty zeroes! On a scale on Earth, that would weigh 4 1/2 nonillion pounds — and totally squash us all.

Wee ones: The Sun is really a giant ball, which looks like a circle from the side. Can you find any ball shapes in the room? How many?

Little kids: Along with the Sun and Jupiter, we can see Mercury, Venus, Mars, Saturn and the Moon without binoculars or telescopes. How many sky objects is that? Bonus: The days of the week are named after them, like SUN-day. The 4^th day of the week is named after Mercury in other languages. Which day is that?

Big kids: If Earth is 8,000 miles wide and Jupiter is about 10 times as wide, about how wide is Jupiter in miles? Bonus: Then about how wide is the Sun in miles?

The sky’s the limit: Our moon is only about 2,000 miles wide. How many moons wide is the Sun?

Answers:
Wee ones: Different for everyone…you might have a toy ball, a globe or a marble.

Little kids: 7 sky objects. Bonus: Wednesday (miercoles in Spanish, mercredi in French).

Big kids: About 80,000 miles. Bonus: About 800,000 miles.

The sky’s the limit: 400 times, since Earth is 4 times as wide as the Moon and the Sun is 100 times as wide as we are. Every Earth-width “chunk” has 4 moon widths in it.

Pearls Are for the Birds

Laura Overdeck — Mon, 07 Sep 2026 06:00:00 +0000

The oyster may look like just another slimy sea creature with a shell. But some oysters hold a prize inside: a pearl. When a scratchy grain of sand gets inside, the oyster coats it with smooth stuff called “nacre.” The layers build for up to 6 months to make a shiny pearl. This bird, called an oystercatcher, probably doesn’t know all that. It just cracks open oysters to eat them – and apparently to make necklaces!

Wee ones: Who makes a pearl faster, an oyster that takes 4 months or one that takes 7 months?

Little kids: If the oystercatcher catches 8 oysters and 3 are holding pearls, how many aren’t? Bonus: If the oystercatcher needs 16 pearls in total, at least how many more oysters does he need to find?

Big kids: Oystercatchers lay 2-3 eggs in one “clutch” (batch of eggs). If an oystercatcher makes necklaces for all 3 of its kids with 10 pearls on each, how many pearls does it need? Bonus: If instead it finds 26 pearls, how many pearls at most can each necklace have if all 3 have to be the same? Will there be any pearls left over?

Answers:
Wee ones: The oyster that takes 4 months.

Little kids: 5 oysters. Bonus: 13 more, since he has only 3 to start.

Big kids: 30 pearls. Bonus: The necklaces can have 8 pearls apiece at most, since 9 apiece would need 27 pearls in total. There will be 2 unused pearls out of the 26.

Meet the Mola Mola

Laura Overdeck — Sun, 06 Sep 2026 06:00:00 +0000

The mola mola fish, or sunfish, is in fact a fish, but looks more like an alien from outer space. This squashed, Frisbee-shaped sea creature can weigh up to 5,000 pounds and can grow to over 10 feet long! What’s even weirder is that sunfish carry around 40 kinds of tiny bugs called parasites on their scales. They let other weird fish (like half-moon fish) eat the parasites. None of this sounds tasty, but it keeps everyone happy.

Wee ones: If you find a 10-foot sunfish and your car is just 1 foot longer, how long is your car?

Little kids: If a 2,000-pound mola mola runs into an even yuckier-looking 5,000-pound one, how much heavier is the bigger fish? Bonus: Do they weigh more together than your 4,000-pound car?

Big kids: Sunfish love to eat jellyfish, but also eat squid, shrimp, and crab, among other things. If a sunfish eats 40 of each of those, how many animals did it eat? Bonus: Most sunfish are only about 6 feet long, and about 6 feet tall, too, since they’re almost circular. About how much taller than you is the sunfish in feet and inches? (Or if you’re taller, how much taller are you?)

Answers:
Wee ones: 11 feet.

Little kids: 3,000 pounds. Bonus: Yes, since together they weigh 7,000 pounds.

Big kids: 160 animals. Bonus: Different for everyone…the sunfish is about 72 inches tall, so subtract your height in inches from 72 or subtract 72 from your height.

Ice Cream on Wheels

Laura Overdeck — Sat, 05 Sep 2026 06:00:00 +0000

As summer ends, let’s give a big thank-you to Harry Burt, who in 1920 figured out how to coat ice cream in hardened dark chocolate. Thanks to him, suddenly people could drive ice cream around in trucks! So our fan Lisa B. asked, how many bars and popsicles does an ice cream truck sell in 1 day? Well, at a park or beach a truck can unload 20-30 bars to one crowd. After 10 stops like that, a truck could sell 200 to 300 bars in a day. And we’re happy to stand in line for one.

Wee ones: Lots of ice cream bars look like rectangles. How many sides does a rectangle have? Is the floor of your room a rectangle?

Little kids: If a driver sells 4 ice cream sandwiches and 2 popsicles, how many ice cream treats is that? Bonus: If he sells an orange popsicle, then a lemon, then a cherry, then orange, lemon, cherry…what flavor is the 11^th popsicle?

Big kids: If they keep selling orange, lemon, cherry, then orange to repeat, what flavor is the 25^thpopsicle? See if you can get it without counting up! Bonus: If the truck sells twice as many treats at the second stop as at the first, and sells 60 total, how many did it sell at each stop?

The sky’s the limit: If the driver buys each treat for $1, which way will make more money, selling 20 of them for $5 each or 30 of them for $4 each?

Answers:
Wee ones: 4 sides.

Little kids: 6 treats. Bonus: Lemon.

Big kids: Orange, since it’s the first treat in a new set of 3. Bonus: 20 treats, then 40 treats.

The sky’s the limit: Selling 30 of them for $4. In the first way, selling them for $5 will make $4 extra on each, so 20 treats make $80. Selling for $4 will make only $3 on each, but 30 of those will make $90 total.

Dog for a Day

Laura Overdeck — Fri, 04 Sep 2026 06:00:00 +0000

If you have a dog and you go away this weekend, you might need someone to take care of your pooch while you’re away. But then there are people who work all week and wish they had a dog only on the weekend. Hey, wait — they could just share your dog with you! And people really do this. There are dog-share companies out there who help people come together to take turns keeping a dog. Sometimes whole groups of people swap the same dog around and around. It’s a great idea: the dog always gets food and playtime and attention, and everyone gets to play with a pet. It works out perfectly — well, depending on the dog…

Wee ones: If you take care of a dog, then your friend gets the dog, then you get the dog, then your friend gets the dog…who gets the dog next?

Little kids: If you get the dog on a Friday and give the dog back 2 days later, on what day does that happen? Bonus: If you get the dog on Thursday from someone who got it 2 days before that, when did that person get the dog?

Big kids: If you and 5 friends all share Rufus, and each of you gets him for 5 days, how many days does Rufus get shared? Bonus: If you don’t feed Rufus enough and he chews through your $250 carpet and $80 of your clothes, how much did Rufus cost you?

Answers:
Wee ones: You get the dog next!

Little kids: On Sunday. Bonus: On Tuesday.

Big kids: 30 days, since 6 people are sharing him. Bonus: $330.

Neighborhood Hot Spot – for Real

Laura Overdeck — Thu, 03 Sep 2026 06:00:00 +0000

You know how sunshine can bounce off glass windows into our eyes? Well, a skyscraper in London, England reflects light so strong and hot that it melts things. Car doors and mirrors have melted, store carpets have caught on fire, and even stone steps have cracked in the heat. It’s because the side of the building is curved, so the windows bounce all the sunlight into one small point (like when you see yourself upside down in a spoon). When you build a building, you’d better do the math first!

Wee ones: The walls of your room are probably straight. How many straight walls can you count around you?

Little kids: If the building melts 2 car doors, 2 tires, 2 side mirrors and a candy bar, how many items did it melt? Bonus: If you park your car at 11:00 and it starts melting an hour later, at what time is that?

Big kids: If it takes 42 minutes for the danger spot to start melting your car, and you parked half that amount of time ago, how many minutes until your car starts melting? Bonus: If a new car parks in the danger spot every 1/2 hour, how many cars are in danger in 12 hours of sunshine?

Answers:
Wee ones: Most rooms have 4 straight walls, but you might have more than that – or a curved one!

Little kids: 7 melted things. Bonus: At 12:00 noon.

Big kids: 21 minutes. Bonus: 24 cars.