A corn cob (see in figure), shaped somewhat like a cone, has the radius of its broadest end as 2.1 cm and length as 20cm. If each `1\ c m^2` of the surface of the cob carries an average of four grains, find how many grains you would find on the entire cob?

Explanation

CSA=`pirl`

=`22/7*21*sqrt(20^2+2.1^2)`

=`132.76cm^2`