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 Posted: Wed Dec 05, 2012 6:54 pm

Joined: Mon Nov 28, 2011 12:24 pm
Posts: 160
How many 3 cm cubes can be made by cutting up a block 12 cm x 24 cm x 18 cm???

My instincts are to divide each number by 3....
Giving an answer of 4 x 8 x 6....

But am I wrong?

And how do I explain to DD????

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 Posted: Wed Dec 05, 2012 7:01 pm

Joined: Mon May 16, 2011 1:05 pm
Posts: 4019
Dpends what you mean by 3 cm cubes. Do you mean a 3x3x3 cube? In which case you are right.

Your best bet might be draw it out persectivelybif you can or find enough cubes (maybe lego could be used.?) to demonstrate it.

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 Posted: Wed Dec 05, 2012 7:30 pm

Joined: Fri Sep 15, 2006 8:51 am
Posts: 8113
or imagine it is a cake or block of cheese... imagine cutting it into 3cm slices first

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 Posted: Wed Dec 05, 2012 8:36 pm

Joined: Fri Oct 12, 2007 12:42 pm
Posts: 3813
You are correct. I would suggest that you explain to DD how many cubes fit in the lenght of the box, how many fit in the width of the box and then how many would fit going upwards.

I used to teach this by using the idea of cubes of chocolate. A box of choccies is very familiar to children and they can form a picture in their mind. The height represents the number of layers in the box.

This box can fit 4 along the side, has 8 rows and 6 layers. 192 delicious chocolates to choose from. Mine are all cubic Bitter Mints. Guess what I got for Christmas!

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 Posted: Wed Dec 05, 2012 9:41 pm

Joined: Mon Nov 28, 2011 12:24 pm
Posts: 160
Love these ideas... thanks!!!! Going off to have a choc or too to demonstrate model to myself!!

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 Posted: Thu Dec 06, 2012 2:56 pm

Joined: Tue Jul 21, 2009 9:56 pm
Posts: 8228
What did the question actually say?

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 Posted: Thu Dec 06, 2012 3:03 pm

Joined: Tue Jul 21, 2009 9:56 pm
Posts: 8228
Also, why not get her to work the method out for herself by giving her an easier example first, which is very easy to draw out, and then making the numbers bigger.

For example, how many cubes 2cm by 2cm by 2cm would fit in a box 2cm by 4cm by 8cm?

I like Herman's idea of slicing it if drawing it in perspective doesn't really help her.

Use sugar cubes?

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 Posted: Thu Dec 06, 2012 10:30 pm

Joined: Mon Nov 28, 2011 12:24 pm
Posts: 160
I'm going to do it with a block of cheese! And chop it up...... though think the Cube will get smaller as we "work"!

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