Our fan Chryssa Z. asked, are there more people or fish in the world? After all, 2/3 of our planet is covered by water. Then our friend Lora S. asked how many birds there are. Turns out the sea has 10 billion tons of fish, which is 20 trillion pounds. That would give us 400 *billion* 50-pound fish, far more than us 8 billion people. And if fish weighed only 10 pounds each on average, we have 2 trillion fish. Meanwhile, scientists think there are between 200 and 400 billion birds. So if you’re looking for a pet, there are plenty of birds and fish to go around!

*Wee ones:* If your neighbor has 2 pet birds and 5 pet fish, does she have more birds or fish?

*Little kids:* If you have a pet bird and a pet fish, how many legs do you and your pets all have together? *Bonus:*How many more birds would you need to have 10 pets in total?

*Big kids:* If there were 4 million whales and twice as many dolphins, how many would we have in total? *Bonus:* If the number of birds doubles every 100 years, and we now have 400 billion, how many birds would there have been 200 years ago?

*The sky’s the limit (for real):* If we have 200 billion birds and 8 billion people, how many pet birds could each person have if we split them up evenly?

Answers:

*Wee ones:* More fish.

*Little kids:* 4 legs, since the fish has none. *Bonus:* 8 more birds, since you start with 2 pets.

*Big kids:* 12 million, since you add in 8 million dolphins (but the real whale number is a lot lower). *Bonus:* 100 billion, since it would have multiplied by 2 twice to get to 400.

*The sky’s the limit (for real):* 25 birds per person!