In the figure, from a rectangular region ABCD with AB = 20 cm, a right triangle AED with AE = 12 cm and DE = 9 cm is cut-off. On the other end, taking BC as diameter, a semicircle is added. The perimeter of shaded region is?
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In right △AED, using Pythagoras theorem,
AD
2
=AE
2
+DE
2
=9
2
+12
2
=81+144=225cm
⇒AD=
225
=15cm=diameter
Required area = ar. ABCD + ar. semi-circle - ar △AED=(20×15)+
2
1
×
7
22
×(
2
15
)
2
−
2
1
×9×12
=300+88.3928−54=334.3928cm
2
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