If the radii of umbra and penumbra cast by an object on a wall are of the ratio 2:6, what is the area of the penumbra ring around the umbra of the latter’s radius is 40 cms?	Options:
A) 40288.57cm^2 B) 40388.57cm^2 C) 40488.57cm^2 D) 40588.57cm^2 E) 40688.57cm^2
et the radius of umbra and penumbra are 2k and 6k.   Then as given radius of umbra=40cm   so 2k=40   k=20   radius of penumbra=20*6= 
<gadget id="calculator">20*6</gadget>
<output>120</output>
120   area of penumbra ring around the umbra=area of penumbra-area of umbra   22/7*[(120)^2-(40)^2]   =40288.57cm^2   40288.57cm^2NSWER:40288.57cm^2
<result>A</result>
If the radii of umbra and penumbra cast by an object on a wall are of the ratio 2:6, what is the area of the penumbra ring around the umbra of the latter’s radius is 40 cms?