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# help my math homework is weird

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Heres the question:

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The solids are similar. Find the volume of the red solid.

The picture isn't working so heres what it looks like:

The blue solid has a square base. Both sides of this base are 21mm long and it says the volume is 5292

The red solid also has a square base. Both sides of this base are 7mm long.

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I got 1764mm3 but when I went to check my answer it said that I was wrong.

plz help.

Guest Apr 3, 2017
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#1
+5546
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I think this is what the picture probably looks like:

Since the boxes are similar, I knew that the height of the red box was h/3.

volume = length * width * height

5292 cubic mm = 21 * 21 * h

Solve for h:

h = 5292 / 441 = 12 mm

red box volume = 7 * 7 * (12/3)

red box volume = 196 cubic mm

Also,

since you are reducing 3 dimensions by 3,

the new volume = old volume / 33

the new volume= 5292 / 27 = 196 cubic mm

hectictar  Apr 4, 2017
#2
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O yeah. So sorry. I forgot to mention this and it is going to be really stupid but they are square pyramids, should've mentioned that. Sorry again!​​​​​​​​​​​​​​

Guest Apr 4, 2017
#3
+1

okay. this is going to sound even more stupid.

So I go to the question and put in your answer just for grins even though they are clearly square pyramids, check your answer, and it's right!

There must have been a glitch.

Guest Apr 4, 2017
#5
+5546
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Holy cow! That is a loooooooooong link...   Lol !!

hectictar  Apr 4, 2017
#4
+5546
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Oh no! Haha okay in that case, this is probably what the picture looks like:

volume = (1/3)(area of base)(height)

5,292 = (1/3)(21)(21)(h)

h = 5,292 / 147 = 36 mm

red volume = (1/3)(7)(7)(36/3)

red volume = 196 cubic mm

As you can see, it is the same answer either way.

Because you are reducing 3 dimensions by 3, the volume will reduce by 3, 3 times.

The new volume = old volume / 33

5,292 / 33 = 196

That is all the math you really need to do.

It wasn't really necessary to go through all that work that I showed.

It isn't a glitch!

hectictar  Apr 4, 2017
edited by hectictar  Apr 4, 2017

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