If you’ve ever petted a dog, you know how fun and furry they can be. It’s just not as much fun to pat a person on the head. So our fan Grace C. asked, how many hairs does a dog have? Dogs have about 15,000 hairs on each little square inch of skin. Just to compare, we humans have up to 100,000 hairs on 120-140 square inches of head, which is fewer than 1,000 a square inch. So our pet pooches are a lot furrier. But as we learned recently, dogs don’t even come close to otters, which have a million hairs per square inch! In any case, a square foot has 12 x 12 or 144 square inches, so a dog has around 2,160,000 hairs per square foot…then it just depends how big your dog is!
Wee ones: If you, a dog and an otter are counting hairs, how many of you are hair-counting?
Little kids: If your dog sheds 1,000 hairs a day, how many is that in a week? Count up by thousands! Bonus: If you brush out your dog every 3 days starting on a Monday, on what days do you brush your pup the next 2 times?
Big kids: If a Dalmatian has your usual 15,000 hairs per square inch, but a Chocolate Lab has twice as many, how many does the lab have? Bonus: If a whole dog has 1,000 square inches of fur (about 6 square feet) and 15,000 hairs per square inch, how many hairs are on the whole dog?
The sky’s the limit: If a poodle has 15,000 hairs per square inch and a husky has 83,000 per square inch, and your beagle is halfway between, how many hairs does your beagle have?
Wee ones: 3 of you.
Little kids: 7,000. You have 1,000, then 2,000, 3,000, 4,000, 5,000, 6,000, 7,000. Bonus: On Thursday, then on Sunday.
Big kids: 30,000 hairs per square inch. Bonus: 15,000,000 hairs, which is 15 million!
The sky’s the limit: 49,000 hairs per square inch. Setting aside the thousands, you need the number halfway between 15 and 83. They are 83-15=68 apart, so the halfway mark is 34 more than 15 and 34 less than 83. That gives us 49 either way.
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.