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PostPosted: Sun Sep 07, 2008 1:20 pm 
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Joined: Thu Aug 16, 2007 8:40 pm
Posts: 5
Dear all,
Please, could you help with this question.

(The picture given is like a photo frame- one rectangle inside another. The outer rectangle's sides are 1.6 m and 2.4 m. The inner rectangle is labeled Plain tiles, and the frame is labelled Border tiles).

Masih is going to tile a floor which is 2.4 m by 1.6 m.
All the tiles are 20 cm square.
He is going to put one layer of border tiles around the edge.
How many tiles does he need to fill in the middle?

The answer is 60. But how do you work it out? Thanks.


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PostPosted: Sun Sep 07, 2008 3:13 pm 
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Joined: Tue Dec 13, 2005 12:49 pm
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Location: berkshire
If you look at the diagram you can see that the inner rectangle will be 2 tiles shorter and 2 tiles narrower than the outer triangle i.e. 2 x 20 cm giving 40cm narrower and shorter.

Therefore 2.4 less 40cm = 2m and 1.6 less 40cm = 1.2

The inner triangle would be 2m x 1.2m (or 10 tiles by 6 tiles) giving 60 tiles.


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PostPosted: Sun Sep 07, 2008 4:00 pm 
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Joined: Thu Aug 16, 2007 8:40 pm
Posts: 5
Thanks, Chad.
Yes, the inner rectangle is 2 tiles shorter and 2 tiles narrower than the outer rectangle.
But we can not say that it is 40 cm narrower and shorter because we do not know how much the side of each tile is.
What we are given is that an area of each tile is 20 cm square, so each side can not be 20 cm in length.
I have been trying to work this out since yeasterday, and it did not make sense with the information given.
I have concluded that there must be a mistake, and the info given should state that each tile's side is 20 cm, not each tile's area is 20 cm square. Then you can work out the answer in this way.


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PostPosted: Sun Sep 07, 2008 4:08 pm 
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Joined: Thu Aug 16, 2007 8:40 pm
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You know what...
It's as simple as that!
...tiles 20 cm square mean that all tiles are square shape with 20 cm each side. But when I looked at the word 'square' I thought of an area, not a shape.
More you look, less you see.


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PostPosted: Sun Sep 07, 2008 7:05 pm 
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Joined: Wed Jan 02, 2008 12:18 pm
Posts: 490
Location: kent
Yes I would have learned this phraseology at school - something 20 cm square but how many people would be taught it these days. It's another example of the old-fashioned stuff that pops up in the 11+ that has nothing to do with IQ.


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PostPosted: Sun Sep 07, 2008 7:15 pm 
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Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11952
It's a very common way of talking about the dimensions of a square -

For an area you would say 20 cm squared or 20 square cm.


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PostPosted: Sun Sep 07, 2008 9:04 pm 
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Joined: Thu Aug 16, 2007 8:40 pm
Posts: 5
My DD thought of tiles with an area of 20, just like me. I think this type of question could have been better phrased for children.
What could be learnt from this scenario:
If the numbers don't add up or the situation doesn't make sense - try an alternative thinking and look at the question with fresh ideas reading every word again. :idea:
I always tell my children that a solution hides in a question itself. :)


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