Net(s) of a triangular prisms

J

Jignesh77

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Good evening,

I hope you're well and thank you for your help in advance.
My son is in year 6 and he chose two options given in the right-hand side( top and bottom) as shown in the attachment.

The correct answer is the top figure and not the bottom one as he thinks. So basically, only one answer is correct. I don't know why the bottom one is wrong. I couldn't explain why.
I hope it makes sense.
 

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If we assume that the sketches are approximately correct - the triangular faces of the prism would be "equilateral" triangles as opposed to "isosceles" .
 
The bottom one would be an isosceles triangular prism IF the sides joined by the arrow had the same length:

1715029169914.png​

Since they don't, the net won't fit together. That's the only reason this isn't the net of a triangular prism.

It's possible that they are using the term "triangular prism" to mean only one that is equilateral (as many are), in which case that would be another reason the top figure is correct. But that is not part of the actual definition, as illustrated, for example, in this site.

In the top figure, the sides that have to match, do:

1715029688602.png​

But your son navigated the most important issues correctly. This is just a detail, either way.
 
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