Dogs in Charge

Here's your nightly math! Just 5 quick minutes of number fun for kids and parents at home. Read a cool fun fact, followed by math riddles at different levels so everyone can jump in. Your kids will love you for it.

Dogs in Charge

January 18, 2015

Lots of dogs get to hang out as people’s pets (and wear costumes, as we saw on Wednesday). But some dogs actually work real jobs, such as police dogs. They’re called the K9 unit, since “canine” means “dog-related,” and they’ve been helping cops and detectives for hundreds of years. K9 unit dogs, who are usually German shepherds like these, help chase down bad guys, sniff for drugs and other materials that break the law, and also work as rescue dogs to find missing people. The dogs can’t talk, so they have to show what they think by doing the right action: barking, or sitting very still next to what they’ve found, and behave at all times. Here in this photo the dogs are working on their self-control by watching a cat without chasing it. K9 dogs train for a few hours every week, and can work for about 6-9 years. Then they get to rest and relax like millions of other pet dogs.

Wee ones: How many dogs can you count in the photo? Count as high as you can!

Little kids: If a dog trains until age 3 and then works for 7 years, how old is the dog when he stops working?  Bonus: If an 11-year old dog has worked for 9 years, how old was she when she started?

Big kids: If a dog starts training at 9:30 each day and goes 8 hours straight, at what time does training end?  Bonus: If 1/5 of those 15 dogs just can’t take it any more and start chasing the cat, how many dogs sit still like they should?

The sky’s the limit: If in self-control training there are 10 times as many dogs as cats, and there are 72 more dog paws than cat paws, how many of each animal do we have?




Wee ones: We can count about 15 in total, but see what you find!

Little kids: 10 years old.  Bonus: At 2 years old.

Big kids: At 5:30 pm.  Bonus: 12 dogs, since 3 dogs pounce.

The sky’s the limit: 2 cats (which have 8 paws) and 20 dogs (which have 80 paws). Doing mental math, for every cat there’s a dog plus an extra 9 dogs, which have 36 paws. So we have 2 such sets of cats and dogs here. To solve with algebra, for c cats and d dogs we have:
4d = 4c + 72
d =10c

Substituting for d in the first equation, we get
40c = 4c + 72
36c = 72
c = 2 So there are 2 cats, giving us 20 dogs.

And thank you Emily B. for sharing this great photo!

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About the Author

Laura Overdeck

Laura Overdeck

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 while still in diapers, 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.

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