xyz block

Geometry Level 4

A 4 × 4 × 4 4\times 4\times 4 grid has just enough material removed such that the front side projects an X , \text{X}, the right side a Y , \text{Y}, and the top side a Z . \text{Z}. The orthogonal views of these letters are shown below.

An isometric view of the final shape is shown below.

What is the volume of this figure?


The answer is 21.333333333.

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1 solution

Jeremy Galvagni
Jun 26, 2018

Here are each of the four layers separated and then color-coded by volume. (They are viewed from above the X so you can see the remains of the Z's from each layer, but they are turned sideways.)

Red: whole unit cubes: 10 of them.

Orange: half cubes: 16 of them.

Yellow: one-third cubes: 4 of them.

Green: one-sixth cubes: 12 of them.

Total volume 10 + 16 2 + 4 3 + 12 6 = 64 3 21.333333 10+\frac{16}{2} +\frac{4}{3} +\frac {12}{6} = \frac{64}{3} \approx \boxed{21.333333}

Interestingly, exactly one-third of the original cube remains.

My answer is 22, this problem needs a great sense of 3-dimensional feeling.

Kelvin Hong - 2 years, 11 months ago

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Indeed, imagine you have to draw the figure with the projections, and with no colors.

Alex King - 2 years, 11 months ago

@Jeremy Galvagni Can you show the centre of the block in the isometric view. It seems like the one u attach do not depict the center of the figure completely. I would like to understand more. Thanks.

donglin loo - 2 years, 11 months ago

I made the Tinkercad design public, so anyone can view it and pull it apart. https://www.tinkercad.com/things/2367ALldVxS

Jeremy Galvagni - 2 years, 11 months ago

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Superb. Superb.

Leonblum Iznotded - 2 years, 10 months ago

That's amazing. Thanks!

donglin loo - 2 years, 11 months ago

It's really tough

Prithwish Guha - 2 years, 7 months ago

I don't colour code the thing, but I also did it layer by layer, and imagine my surprise when it was right in the first try with my first time doing this kind of puzzle. I have a similar one, though it's definitely easier since mine is all blocky (just like your red ones) with silhouettes from two sides (yes, X and Y but no Z). Anyone with any interest in mental imaging, please do come and enjoy!

Saya Suka - 4 months ago

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