3. The Fuel Crisis Problem

2 May
maths with zombies

…because everything’s better with zombies!

You hear the first reports on the news that the dead have started to rise and attack the living. You knew this was going to happen and you’re ready. You grab your ‘bug out bag’ and a baseball bat before leaping into your car. The safe house you’ve been carefully preparing and provisioning for the last year is 74 miles away and if you drive fast enough you’ll be there in an hour at the most; then you’ll be safe. As you start your engine you glance at the fuel gauge and realise your room mate’s not only borrowed your car yet again without asking, but he’s also not topped up the tank so it’s only a quarter full. You know your tank holds 11 gallons when it’s full and your car does 27 miles to the gallon. What do you do?

A:I’ve got enough fuel to get there, so I’m leaving the city while I still can.

B:There’s not enough fuel left in the tank. I’ll need to get some more before I head off. It’ll be risky but at least I won’t end up stranded in the middle of nowhere when I run out.

Scroll down to see the right answer…

What answer did you get?

A: Well done, you made the right decision. You must have correctly worked out you have enough fuel to go 74.25 miles before you run out and that’s just enough to get you to your safe house.

B: Oooh, poor choice. You have enough fuel so you should leave immediately. Enjoy fighting off the zombie horde as you waste time trying to find more fuel.

How to work it out: You first need to work out how much fuel you have left in the tank. This is the size of the tank (11 gallons) divided by how much is left in it (1/4) and is 2.75 gallons. Next you need to work out how far you can go on this much fuel. This is done by multiplying the number of miles your car can do per gallon (27) by the amount of fuel you have left (2.75 gallons). This gives you 74.25 miles. Finally, subtract the miles you have to travel from this distance (74.25 – 74). If this number is positive ( as in this case where it’s 0.25), you’ve got enough fuel to get you there. If it’s negative, you haven’t. This would be the case if the miles per gallon was only 0.5 lower: (2.75 * 26.5) – 74 = -1.125, so you’d run out of fuel just over a mile from your safe house. If that were the case, you’d be better selecting option B.

Note: 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.

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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