Two parallel sides DC & AB of a trapezium are 12 cm & 36 cm respectively. If the non-parallel sides are each equal to 15 cm, how do I find the area of the trapezium?

Thanks,

Ron

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- January 27th 2011, 08:29 AMrn5aArea Of Trapezium
Two parallel sides DC & AB of a trapezium are 12 cm & 36 cm respectively. If the non-parallel sides are each equal to 15 cm, how do I find the area of the trapezium?

Thanks,

Ron - January 27th 2011, 09:05 AMBAdhi
draw perpendicular lines from D and C to the line AB you'll find them equal, then find the length of those drawn lines by using the right angle triangle which was created by the drawn line(s).

- January 27th 2011, 04:29 PMrn5a
Suppose the perpendicular lines drawn from D & C to AB meet AB at E & F respectively. Then EF is 12 cm but how much is AE & BF? I need AE or BF to find DE or CF & then use pythagoras theorem.

Thanks,

Ron - January 27th 2011, 05:08 PMHallsofIvy
The shorter base, from D to C, is 12 cm long. The distance between the bases of those two perpendiculars (lets call them E and F) is also 12 cm. That means the two pieces

**outside**E and F total 36- 12= 24 cm. And looking at the right triangles formed at the ends by those perpendicular, "HL" tells you the two pieces are each length 12. Now, use the Pythagorean theorem.