In the figure, ABCD is a rectangle, AZ=WC=6 units, AB=12 units and the area of trapezoid ZWCD is 120 square units. What is the area of triangle BQW?
Since the area of the trapezoid ZWCD is 120
The height of this trapezoid is AB and the bases are ZD and WC
We have
120 = (1/2) AB (ZD + WC)
120 = (1/2) 12 ( ZD + 6) multiply through by 2
240 = 12 (ZD + 6) divide both sides by 12
20 = ZD + 6 ubtract 6 from both sides
14 = ZD
Now angle DBW = angle BDZ
And angle ZQD = angle BQW
And since AZ = WC
Then ZD = BW
So by AAS....triangle ZQD is congruent to triangle WQZ
And the altitude of trangle DQZ = altitude of triangle BQW
And since twice these altitudes = AB....then each altitude = 1/2(AB) = 6
So....the area of triangle BQW =
(1/2) BW * altitude of BQW =
(1/2) (14)(6) =
(1/2) (84) =
42 units^2