Saturday, January 11, 2014

If a trapezoid has a top base of 6 and a bottom base of 30 and a height of 15, what is its area?

For a REGULAR Trapezoid (sides EQUAL) ---> A or
B


>>> METHOD
A-


You need to think of the imaginary lines which come down
as the perpendicular from the TOP and hit perpendicular to the
bottom.


See them
yet?~@


Cutting along those lines, that leaves you with ONE
rectangle 6 by 15 [units] and two triangles with height 15 and *___
base.


One of those triangles could be cut loose from the
rectangle and rotated so that the hypotenuse [long side] joins to its twin. Now you
COULD do the area for two indentical triangles, BUT one rectangle is just as
easy.


NOW, add the areas together (6 x 15) + (15 x *___) =
Area of Trapezoid


** It is YOUR homework, so YOU figure out
what is left and take half that fill in the blank and get the whole
answer.


~@ If you have trouble visualizing it, make a
template out of graph paper, and cut your lines. Superimpose the trapezoid on the grap
paper grid; 6 top, 15 down, base 30
(centered)



>>>>
METHOD B-


MENTALLY, (or actually on a grid ) Cut the
trapzoid down the center on a perpendicular. Rotate and flip the pieces so that the
diagonal sides meet and you SHOULD be able to see an NEW Rectangle from the pieces, and
THEN find the area easiest.



++++ IRREGULAR
Trapezoid (Unknown/Uneven sides)


You need to take the AREA
of two triangles made from the figure cut on a diagonal from one corner to the opposite
corner {Trap- ABCD, diagonal from corners A-C}


See it in
your head yet?


NOW you should be on easy street AND better
understand why there IS a formula for the trapezoid area (which must be paraphrased by
this discussion limitations):


1/2(Btop)(H) +
1/2(Base)(H)



^^^^


OK,
so I explained how to MAKE the CLOCK instead of telling you what time it was! Give them
all a go, find your favorite explanation and USE it!


ONE
problem does not always have ONE solution.

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