Posted by leena on .
in the diagram AB=20 cm, BC=21 cm, AD=10 cm and DE= 10.5 cm. Angles ABC and ADE are right angles. if triangleADE is removed from triangleABC.What is the area of shaded region that remains?

geometry 
Graham,
Missing information: presumably A, D, B are colinear.
For right angle XYZ, ∆XYZ=(1/2)(XY×YX)
So:
∆ABC∆ADE = (1/2)(AB×BC)(1/2)(AD×DE)