When hot lava explodes from a volcano, it can melt just about anything in its way – but not diamond. So some cooled lava rocks have diamonds inside them! You’d have to sort through about 250 dump trucks of lava to find 1 carat of diamonds (1/141 of an ounce). But there are other materials inside lava, too. If you buy lava rocks, put a rock in a sock and smash it with a hammer (with a grown-up’s help). We found chips of white quartz in ours. See if you find anything!
Wee ones: If you have 1 lava rock and 2 regular rocks, how many rocks do you have?
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 can find one diamond in every 25 dump trucks of lava, how many should you find in 100 trucks? Bonus: 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?
Answers:
Wee ones: 3 rocks.
Little kids: 5 rocks. Bonus: 9.
Big kids: 4 diamonds, since you have 4 sets of 25 trucks. Bonus: At least 9 rocks must have both diamond and gold. 22 diamond rocks + 27 gold rocks = 49 rocks. Since there are only 40 rocks, at least 9 must have both diamond and gold.
