A hemi-spherical bowl has 3.5 cm radius. It is to be painted inside as well as outside. The cost of painting it at the rate of Rs.5 per 10sq. cm. will be :

Explanation:

According to the question,

Radius = 3.5 cm

⇒ In the question it is given that A hemi-spherical bowl is to be painted inside as well as outside

Total area that is to be painted

= Inside area of bowl + outside area of bowl

=2πr^2+2πr^2=4πr^2

=4×22\7×7\2×7\2cm^2

⇒ Painting Rate = 10cm^2 in 5 Rs.

1cm^2 will be painted =5\10

=Rs.1\2

So total cost will be painted in

4×22\7×7\2×7\2×1\2=Rs.77