Maths Question - Teacher incorrect?

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wombat1
Posts: 38
Joined: Thu Apr 23, 2009 11:00 pm

Maths Question - Teacher incorrect?

Post by wombat1 »

Daughter's teacher has given this question and supplied answer that I believe to be incorrect. Be interested to have any expert opinions (won't give you teacher's answer or mine yet so as not to lead you down one path or another).

Q. How many panes of glass 35cm x 25cm can be cut from a sheet of glass 1m x1m?

Many thanks!
yoyo123
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Location: East Kent

Re: Maths Question - Teacher incorrect?

Post by yoyo123 »

just quickly would say 10

you can get 4 x25cm from 1m, but only 2 of the 35cm from 1m width

there is a long strip of 30cm by 1m, you can cut 2 more from this
moved
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Joined: Fri Oct 12, 2007 1:42 pm
Location: Chelmsford and pleased

Re: Maths Question - Teacher incorrect?

Post by moved »

I agree with yoyo. These types of problems are easiest when drawn. Will you tell us the answers now?
narshad1
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Joined: Mon Aug 02, 2010 12:35 pm

Re: Maths Question - Teacher incorrect?

Post by narshad1 »

11
wombat1
Posts: 38
Joined: Thu Apr 23, 2009 11:00 pm

Re: Maths Question - Teacher incorrect?

Post by wombat1 »

Thanks for your replies.

I too came up with 10 - after drawing a diagram.

The teacher has told them to divide 10000 sq cm by 875 sq cm (10000 sq cm = 1 sq m; 35cm x 25cm = 875 sq cm) giving an answer of 11.

Love to know how she intends to make the 11th pane of glass from the leftover bits!
pheasantchick
Posts: 2439
Joined: Tue Jun 02, 2009 10:28 pm

Re: Maths Question - Teacher incorrect?

Post by pheasantchick »

The 11th pane is a broken pane! The question doesn't say anything about complete panes!
JaneEyre
Posts: 4843
Joined: Sun May 09, 2010 1:04 pm

Re: Maths Question - Teacher incorrect?

Post by JaneEyre »

wombat1 wrote:Thanks for your replies.

I too came up with 10 - after drawing a diagram.

The teacher has told them to divide 10000 sq cm by 875 sq cm (10000 sq cm = 1 sq m; 35cm x 25cm = 875 sq cm) giving an answer of 11.

Love to know how she intends to make the 11th pane of glass from the leftover bits!
I am annoyed because I get also 11 and not 10 like you :(
I do it through a mathematical way, without drawing...
The area of the sheet of glass is: 100x 100 = 10 000 sq cm
The area of one pane of glass is: 35cm x 25cm = 875 sq cm

So I divided the area of the big sheet of glass by the area of one pane (long division, sorry, I can't find the horizontal line above the dividend and for the subtraction. How can I do that?):
11
___________
875 | 10000
-875
_____
1250
-875
_____
375


so that makes 11 panes of glass and there is a reminder...

Is it really important to work with a diagram and find 10? I am at a loss now? :cry:
JaneEyre
Posts: 4843
Joined: Sun May 09, 2010 1:04 pm

Re: Maths Question - Teacher incorrect?

Post by JaneEyre »

Oh gosh, when I sent my message, all the alignment of my division disappeared!!! :evil: :evil:

Well, you can do the division yourself on a piece of paper and understand what I meant :lol:
999 mum
Posts: 422
Joined: Sun Feb 14, 2010 12:02 am

Re: Maths Question - Teacher incorrect?

Post by 999 mum »

JaneEyre - why are you annoyed?

Isn't this one of those questions where you need to consider the rest of the info provided?

(a coach can carry 50 people, 75 students are going on a school trip, how many coaches are needed?
75/50=1.5, but the answer is 2)
hermanmunster
Posts: 12815
Joined: Fri Sep 15, 2006 9:51 am
Location: The Seaside

Re: Maths Question - Teacher incorrect?

Post by hermanmunster »

JaneEyre wrote:
wombat1 wrote:Thanks for your replies.

I too came up with 10 - after drawing a diagram.

The teacher has told them to divide 10000 sq cm by 875 sq cm (10000 sq cm = 1 sq m; 35cm x 25cm = 875 sq cm) giving an answer of 11.

Love to know how she intends to make the 11th pane of glass from the leftover bits!
I am annoyed because I get also 11 and not 10 like you :(
I do it through a mathematical way, without drawing...
The area of the sheet of glass is: 100x 100 = 10 000 sq cm
The area of one pane of glass is: 35cm x 25cm = 875 sq cm

So I divided the area of the big sheet of glass by the area of one pane (long division, sorry, I can't find the horizontal line above the dividend and for the subtraction. How can I do that?):
11
___________
875 | 10000
-875
_____
1250
-875
_____
375


so that makes 11 panes of glass and there is a reminder...

Is it really important to work with a diagram and find 10? I am at a loss now? :cry:
Trouble is your are trying to work out how many 875 sq cm shapes you can get regardless of their shape - the question has a specific shape mentioned. Bit like the crucial bus - you can't have a half a bus
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