Lots of animals love to make noise, as we talked about the other day. But one of the coolest might be the dolphin. Our fan Mia G. asked, how far does a dolphin’s sound travel? (and sent this awesome drawing!) It turns out dolphins make all kinds of sounds: clicks, squeaks, whistles, and creaking noises. Bottlenose dolphins make as many as 2,000 squeaks per second; the sounds bounce off objects, telling the dolphins how far away they are. This works best within 700 feet. Along with that, dolphins make clicking sounds to talk to each other, and every dolphin makes its own special whistle sound that is different from all others’ (like fingerprints on us humans). Now the trick is to figure out what they’re saying!

*Wee ones:* If there are 5 dolphins in a “pod” (group) and 1 dolphin has a baby, how many dolphins are there now?

*Little kids:* If you get to feed the dolphins every other day starting on Sunday, what other days that week do you feed them? *Bonus:* Dolphins can leap up to 15 feet in the air! How high above your head is that (if you’re standing at pool edge)? Find your height in feet!

*Big kids:* If 20 dolphins are dancing and every 3rd one is waving its left flipper, how many at most could be doing that? (You can pick which dolphin is the 1st waver.) *Bonus:* It takes about 20 seconds to sing the ABCs. How many squeaks can a dolphin make in that time at 2,000 squeaks a second?

*The sky’s the limit:* If a dolphin creaks twice, whistles 3 times, then clicks 4 times, then creaks twice again to start the pattern again, what’s the 200th sound it makes?

Answers:

*Wee ones:* 6 dolphins.

*Little kids:* Tuesday, Thursday and Saturday. *Bonus:* Different for everyone…subtract your height in feet from 15.

*Big kids:* 7 dolphins, if the 1st or 2nd dolphin waves (if it starts with the 3rd, the 18th will be last and you’ll have only 6). *Bonus:* 40,000 squeaks.

*The sky’s the limit:* A creak. The dolphin makes sounds in sets of 9, so you can find the biggest multiple of 9 that’s less than 200, then count up. Cool trick: multiples of 9 have digits that always add up to 9 or a multiple of 9. 198 is the biggest multiple less than 200, so the 200th sound is 2 sounds into the next set, which is a creak. Another way to find it: we know 18 is a multiple, and so is 180, then 189 and 198.

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.