Today from Bedtime Math: Whatever Floats Your Boat

Hey, why are those stuffed animals floating around in the kiddie pool? Well, because it's a beautiful summer day, and because they can. They're floating on simple tin-foil boats, which the animals don't weigh enough to sink. When you float an object on a boat, the boat will sink just enough so that the water it "displaces," or pushes out of the way, weighs the same as that object. If something weighs 1 pound, the boat will push 1 pound (16 ounces) of water out of the way, which makes the water level go up. That's why something too heavy will sink the boat too far down and water will gush in over the edges. Yikes! So if you want your floating furry friends to stay dry, weigh them first, then test your boat with the same weight of coins, rocks, or something else to avoid any sinking ships.

Now here's today's math ~

Wee ones: How many stuffed animals are floating in the pool? Count them! (In case you can't see the photo, there's 1 rainbow caterpillar on the first boat and 3 small lobsters on the second.)

Little kids: If the caterpillar weighs 9 ounces and the 3 lobsters each weigh 2 ounces, which boat is displacing more water? Bonus: How much more?

Big kids: If you have 4 stuffed animals that each weigh 5 ounces plus a big fat 1-pound teddy bear, how much do they weigh altogether? (Reminder: a pound has 16 ounces.)  Bonus: If you first test your big animal barge with rocks that each weigh 7 ounces, how many rocks does the boat have to be able to hold to be sure it can float your furry friends?

Answers:

Wee ones: 4 stuffed animals.

Little kids: The caterpillar.  Bonus: 3 more ounces.

Big kids: 36 ounces.  Bonus: 6 rocks, since 5 rocks will only prove that the boat can hold 35 ounces.

And for more ideas about making foil boats and sinking them like pirate ships, check out Amy Hengerer's post on our Add It Up parent blog if you haven't already!