Calling All 5th Graders!

Get Ready to Problem-Solve

One of my favorite strategies I use when problem-solving is to work backwards. So when I think of a problem that almost forces you to work backwards, it gets put into play! This is a volume problem so your students may not be ready yet, but keep it in mind when you're ready to teach volume.

Question: What are the dimensions of the box below?

What we know:

*** The total volume is 54 cubic inches.
*** The box is twice as long as it is wide.

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There are several ways students could approach this problem. They could guess and check, which is a great way to plunge in and begin solving a problem! As a teacher, I would be paying attention to what numbers they begin with. After working with multiplication for awhile, we hope that students understand how quickly, or exponentially numbers can grow when multiplying, so smaller numbers are called for here. 

Another strategy might be to divide 54 by 3 and start there. However,  if the length, width, and height are 16 inches each, the resulting volume would be much larger than 54 inches cubed.

I played around with factoring numbers and working with primes, which was fun, but a little beyond 5th grade standards (not that they couldn't do it!). 

As a fifth grade student, I'm pretty sure I would have worked backwards - first thinking of an even number for the length and half of that number for the width. Say, 8 and 4. Then I would see if I could make the height work. 

This particular problem is great because you can substitute so many numbers to make it more difficult, even sneaking in a decimal!

Have fun!