15. The Out-Running Your Friends Problem

1 Aug
maths with zombies

…because everything’s better with zombies!

There are 37 zombies chasing you and your friends. The zombies are those pesky new fast ones and they’ll quickly catch whoever’s moving slowest. Each time one of your friends gets caught, 3 zombies stop to feast on their brains. How many of your friends do you have to out-run before all the zombies are too busy eating other people to chase you, meaning you can finally get away?

A: 12

B: 13

C: 14

D: 15

Scroll down to see the right answer…









What answer did you get?

A: With only 12 friends down, there will still be 1 more zombie chasing you, so you’ll still have to out-run 1 more friend to escape.

B: Perfect. You might have lost 13 friends, but at least you got away from the zombies

C: That’s one more friends than you need to out run. You did get the maths wrong, didn’t you?

D: Humm, you do like your friends, don’t you?

How to work it out: This is a nice simple one. Each time the pursuing zombies catch someone, the number chasing you goes down by 3. This means all you need to do is divide the number of zombies by 3. In this case, with 37 zombies chasing you, when you divide this by 3 you get 12.33. This means that after 12 of your friends have been caught, there will still be one zombie chasing you (it’s the 0.33), Therefore, one more of your friends has to get caught before you are finally free to escape, so the total number of friends you have to out-run it 13.

While the problems provided here are copyright of Maths With Zombies, if you are a teacher, you can use any of these problems for free in your classes – but please credit Maths With Zombies as the original source (e.g. Downloaded from MathsWithZombies.wordpress.com). You can download a PDF handout of this problem from here.

If you do use this problem in a class, please post a comment here to let me know how you used it and how it was received by your students. These problems cannot be used for any commercial purpose without express written permission.


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From the author of For Those In Peril On The Sea, a tale of post-apocalyptic survival in a world where zombie-like infected rule the land and all the last few human survivors can do is stay on their boats and try to survive. Now available in print and as a Kindle ebook. Click here or visit www.forthoseinperil.net to find out more. To download a preview of the first three chapters, click here.

To read the Foreword Clarion Review of For Those In Peril On The Sea (where it scored five stars out of five) click here.

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2 Responses to “15. The Out-Running Your Friends Problem”

  1. jkholmes92 01/08/2013 at 15:34 #

    If this had been round when I was at school my maths would probably be a whole lot better. 😀

    • cmdrysdale 01/08/2013 at 15:49 #

      I think a lot of people feel that way. It makes it all a lot more entertaining (and useful!) doesn’t it?

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