A pearl is a beautiful, smooth ball from a weird place: the slimy inside of an oyster (or any two-shelled “mollusk”). If a grain of sand gets inside the oyster, the oyster avoids getting scratched by coating the sand with layers of “nacre,” or mother of pearl. That’s the same rainbow-shiny stuff that lines the shell, too. Coating the sand over and over takes a long time, so only a few grains turn into big, shiny balls. That’s why pearls are special, and people make jewelry out of them. So Bedtime Math fan Amber I. asked, what is the world’s longest pearl necklace? Unbelievably, it’s more than a mile long! Made by Guangdong Ronghui Pearls Culture Co., the necklace has 316,474 pearls — that’s 316 *thousand* four hundred seventy-four. It also weighs almost 375 pounds. Very hard to wear!

*Wee ones:* What shape is a pearl?

*Little kids:* If you hold 1 pearl on each tip of your fingers and thumbs, how many pearls do you have? *Bonus:* If you need 5 more to string them around your wrist, how many pearls will you need in total?

*Big kids:* If you added one more pearl to this 316,474-pearl necklace, how many would it have? See if you can remember the rest of the number! *Bonus:* If each pearl is about 1/2 inch wide, how long would a 30-pearl stretch be?

Answers:

*Wee ones:* A circle (its cross-section, looking from the side), or in 3D it’s a “sphere.”

*Little kids:* 10 pearls. *Bonus:* 15 pearls.

*Big kids:* 316,475 pearls. *Bonus:* 15 inches.