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 Post subject: Surface areaPosted: Wed Jan 01, 2014 11:25 pm

Joined: Tue Aug 30, 2011 5:33 pm
Posts: 125
Hi,
Feel bit daft posting this my daughter missed 2 weekly maths lessons at school as she was rehearsing for Xmas concert, the teacher gave her homework sheet 1st week to try which she done it hasn't been marked yet , then 2nd week homework was set online , when she done online work it's marks instantly and they were wrong so here goes......
Work out surface area of toblerone
Each piece (triangle) is 4cm width 4cm height - 1cm depth
Their is 12pieces

So please correct me if wrong triangle 4x4=16 divide by 2 so surface area of triangle front and end is 16 then sides are 4x12=48 x3 = 144 + 16= 160
Does this sound correct?

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 Post subject: Re: Surface areaPosted: Thu Jan 02, 2014 1:15 am

Joined: Wed Jan 18, 2012 11:41 am
Posts: 4584
Location: Essex
Morgan0210 wrote:
Work out surface area of toblerone
Each piece (triangle) is 4cm width 4cm height - 1cm depth
Their is 12pieces

So please correct me if wrong triangle 4x4=16 divide by 2 so surface area of triangle front and end is 16 then sides are 4x12=48 x3 = 144 + 16= 160
Does this sound correct?

The sides are not all 4cm long according to this, though - the base is 4cm and the height is 4cm, which makes the two other sides 4.472cm (possibly rounded to 4.5cm here)

B is the length of the base: 4
A is the altitude (height): 4
L is the length of either of the other two sides

L = Square root of ((A squared) plus (half B, squared))
= Square root of (16 + 4)

(Sorry, can't work out how to do the notation).

So the perimeter of each face is B + L1 + L2 (4 + 4.5 + 4.5) = 13cm, not 12cm.

Or 12.944cm...

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Outside of a dog, a book is a man's best friend. Inside of a dog it's too dark to read.Groucho Marx

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 Post subject: Re: Surface areaPosted: Thu Jan 02, 2014 7:09 am

Joined: Tue Dec 18, 2012 10:59 am
Posts: 3579
Is the toblerone unwrapped...ie work out area of each bit and x 12 rather than in its box? Plus toadie is right, the sides of the triangles are not 4, that is the perpendicular height

If I were you I would definitely buy one so you can both visualise it....and then scoff the lot

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 Post subject: Re: Surface areaPosted: Thu Jan 02, 2014 9:11 am

Joined: Sat Oct 08, 2011 1:25 pm
Posts: 1360
That is a fairly rubbish question, too many assumptions need to be made.. Just eat it

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 Post subject: Re: Surface areaPosted: Thu Jan 02, 2014 10:43 am

Joined: Tue Dec 18, 2012 10:59 am
Posts: 3579

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 Post subject: Re: Surface areaPosted: Thu Jan 02, 2014 1:35 pm

Joined: Wed Jan 18, 2012 11:41 am
Posts: 4584
Location: Essex
Look on the bright side, at least the question totally ignores the bit of chocolate the triangles are joined to at the bottom...

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Outside of a dog, a book is a man's best friend. Inside of a dog it's too dark to read.Groucho Marx

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 Post subject: Re: Surface areaPosted: Thu Jan 02, 2014 2:06 pm

Joined: Sat Oct 08, 2011 1:25 pm
Posts: 1360
And that they have curves...

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 Post subject: Re: Surface areaPosted: Thu Jan 02, 2014 3:46 pm

Joined: Mon Oct 21, 2013 7:59 pm
Posts: 2811
As do I....after all that chocolate....!!!

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 Post subject: Re: Surface areaPosted: Thu Jan 02, 2014 11:06 pm

Joined: Sat Apr 20, 2013 5:27 am
Posts: 241

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