When a volcano blows up, it gushes with glowing red-hot melted rock called lava. It’s hotter than 1300 degrees F, so it can melt just about anything in its way. But one thing it can’t melt is diamond. So some cooled lava rocks have diamonds inside them! Now, there aren’t a lot of diamonds mixed in, so you’d have to sort through about 250 full dump trucks of lava to find 1 carat of diamonds (less than 1/100th of an ounce). But there are specks of other materials inside lava, too. If you ever buy lava rocks for a grill, put a rock in a sock and hit it with a hammer to split it open (with a grown-up’s help). Here at Bedtime Math we smashed 6 lava rocks, and found a chip of white quartz in 3 of them. See if you find anything in yours!
Wee ones: Lava rocks for the grill are about the size of your fist. Find 3 objects in your room about that size.
Little kids: If you smash 6 rocks and 1 has a diamond in it, how many don’t? Bonus: If you buy a bag of 10 lava rocks and count them as you crack them open, what’s the second to last number you say?
Big kids: If you’re cracking open 40 lava rocks, of which 22 have a diamond and 27 have gold inside them, what’s the smallest possible number of rocks that have both? Bonus: If you can find one diamond in every 250 dump trucks of lava, how many should you find in 1,000 trucks?
Wee ones: Items might include small stuffed animals, toy balls, or regular rocks from outside!
Little kids: 5 rocks. Bonus: 9.
Big kids: 9 rocks, since only 18 of the 27 gold ones can have no diamond. Bonus: 4 diamonds, since you have 4 sets of 250 trucks.
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.