Ahhh!!!! Algebra!!

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suttoncoldfield
Posts: 10
Joined: Sun May 13, 2012 2:18 pm

Ahhh!!!! Algebra!!

Post by suttoncoldfield »

Hi,

My dd can't grasp alegbra and consequently is finding it hard to explain this=Area=1/2(a+b)H for the area of a trapezium.Could I please have a clear explanation....Thanks 8)
fast trak
Posts: 44
Joined: Tue Apr 10, 2012 5:24 pm

Re: AHHH!!!!ALGEBRA!!

Post by fast trak »

i think uve to post this in maths forum isnt it. is that from VR? coz i havent come across such a qstn in VR. :?
Guest55
Posts: 16254
Joined: Mon Feb 12, 2007 2:21 pm

Re: AHHH!!!!ALGEBRA!!

Post by Guest55 »

This isn't algebra, it's area!

To find the area of a trapezium you find the average length of the parallel sides and then multiply by the perpendicular distance between them.
fast trak
Posts: 44
Joined: Tue Apr 10, 2012 5:24 pm

Re: AHHH!!!!ALGEBRA!!

Post by fast trak »

Guest55 wrote:This isn't algebra, it's area!

To find the area of a trapezium you find the average length of the parallel sides and then multiply by the perpendicular distance between them.

is this from VR? :?
ConcernedDad
Posts: 204
Joined: Wed Jan 25, 2012 8:43 pm

Re: AHHH!!!!ALGEBRA!!

Post by ConcernedDad »

It is Geometry, not algebra :)

Formula given by both suttoncoldfield and Guest55 is of course correct.

Here is a derivation of the formula for trapezium's area.

Let us say we have a trapezium with two parallel sides (of lengths 'a' and 'b'), and a height of 'H'.

Draw a diagonal across the trapezium i.e. draw a line connecting two opposite vertices. Now, the trapezium looks like a combination of Two Triangles whose base lines are parallel to each other. These triangles have base lengths of 'a' and 'b', and both have the the same height of 'H'.

Area of Trapezium is therefore = Sum of Areas of the Two Triangles
= (aH)/2 + (bH)/2
= (a+b)H / 2

Derivation of Triangle's Area ( 1/2 x base x height) is of course a different story :)

Btw, I just noted this in wikipedia
Wikipedia wrote: The word trapezium has several meanings:
(Outside the US) – a quadrilateral with one pair of parallel sides (a shape known in the US as a trapezoid).
(In the US) – a quadrilateral with no parallel sides (a shape known elsewhere as a general irregular quadrilateral).
Didn't know that a trapezium does not have parallel sides if it is on the other side of the pond. One learns something everyday :)
BusyQueenBee
Posts: 102
Joined: Sat Dec 17, 2011 1:02 pm

Re: AHHH!!!!ALGEBRA!!

Post by BusyQueenBee »

Is this a question for eleven plus maths? :?
Last edited by BusyQueenBee on Mon Jul 09, 2012 10:00 pm, edited 1 time in total.
ToadMum
Posts: 11945
Joined: Wed Jan 18, 2012 12:41 pm
Location: Essex

Re: AHHH!!!!ALGEBRA!!

Post by ToadMum »

I don't know about other areas and without digging out the paper I cannot remember whether the Essex CSSE Maths this time required such knowledge, but the formula is one of the two "you might need to use these" given at the beginning of the SATS Level 4-6 Maths papers.
Outside of a dog, a book is a man's best friend. Inside of a dog it's too dark to read.Groucho Marx
Guest55
Posts: 16254
Joined: Mon Feb 12, 2007 2:21 pm

Re: AHHH!!!!ALGEBRA!!

Post by Guest55 »

They are KS3 papers ... not appropriate for KS2 children as they are based on the KS3 'old' curriculum. They would not be used in KS3 now as they are not focused on the new style of questioning.
AEC
Posts: 9
Joined: Sat Jun 23, 2012 6:07 pm

Re: Ahhh!!!! Algebra!!

Post by AEC »

suttoncoldfield wrote:Hi,

My dd can't grasp alegbra and consequently is finding it hard to explain this=Area=1/2(a+b)H for the area of a trapezium.Could I please have a clear explanation....Thanks 8)

Hi Not to worry mate and it is absolutely great to see dd has been challenged. Just think of 'area' as the space inside the shape and "Area=1/2(a+b)H" will make more sense if you draw a trapezium and label the two parallel length as "a and b" of your choice. All then is required to substitute the appropriate values and obtain a numerical answer.

However, if your dd is struggling with substitution then that's algebra and I would suggest dd should work on that before moving on to Areas which off-course can be done with using letters and just simply do the steps but I think using "Area=1/2(a+b)H" serves a great purpose in enhancing algebraic skills.

Any questions, please do not hesitate to contact.

Regards

AEC
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