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# What is going on in these volume calculations?

I’m stumped. Ideas?

## 6 replies on “What is going on in these volume calculations?”

Howard Phillipssays:

Well, for the first one I added the three side lengths, doubled the result, and subtracted the unit volume, as I knew it involved volume.
The second one I couldn’t get anywhere with!
Seriously, though, the marking scheme should go like this:
Max 3
less 2 for not showing any working
less 2 for getting the wrong numerical answer
less 1 for not getting the units right
Total score -2

I suspect that the author never played with blocks in K-2

Not very likely, but possibly mistaken perimeters?

My guess is perimeter of base, plus height. Where they may have made different choices of which side should be the height… sometimes reusing one of the sides of the base, oops. Hm. 2*(7+4) + 4 seems right for the second one, and the units are even correct for that. 2*(6+5) + 3 would make sense but that’s only 25 feet, not 27. Still, seems like a reasonable idea of what the student was trying to do? Maybe?

This is sort of similar to the “length plus girth” measurement that shipping companies use to figure out whether your box is “large” and has to pay more, right? Except there the length is always the longest side and the girth is the perimeter perpendicular to that. I think.