1. ## Re: Trapezoids

How will I use this proportion?

2. ## Re: Trapezoids

Originally Posted by Idea
CD meets BE at F

AC = BF = a
BE = b

We let h and k be the distances from C and D to the side BE

4 = area BCF - area BDF = 1/2 (h - k) a

Use the proportion

$\frac{k}{b-a}=\frac{h}{b}$
How did you find this proportion?

3. ## Re: Trapezoids

EDF and EAB are similar triangles therefore $\frac{\text{EF}}{\text{EB}}=\frac{k}{h}$

4. ## Re: Trapezoids

I beg your pardon. I am solving nearly 70 questions a day. My brain stopped.

ABE=9
CDA=4
We don't know the area of CFE.
Area of BECD is 5.
To use the above ratio we need the area of FCE or BDE or DFE

5. ## Re: Trapezoids

area BCD = 4 = area ADC

area BCE = 9 = area ABE

6. ## Re: Trapezoids

CD/AB=2/3
DC/DF=2
ABC=ACE
DFE=2
CDE=2
ABC=6
Is that right?

7. ## Re: Trapezoids

Originally Posted by kastamonu
Cd/ab=2/3
dc/df=2
abc=ace
dfe=2
cde=2
abc=6
is that right?
dfe = 1
cde = 2
bdf = 2

abc= 6

8. ## Re: Trapezoids

I made a typo DFE is 1. Many Thanks.

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