Find the Total surface area of a hollow hemisphere whose outer and inner radii are given as  $4·2$ cm and$1·4$ cm respectively.

Find the total surface area of a hollow hemisphere whose outer and inner radii are $4.2$cm and $2.1$cm respectively

Choose the correct answer:

If the curved surface area of a hemisphere is $308 sq. cm$, then its diameter will be _____.

The outer radius of a hollow hemisphere is twice its inner radius. The outer radius of another hollow hemisphere is thrice its inner radius. Find the ratio of the curved surface area of the hollow hemispheres in which the outer radius of the hollow hemisphere is twice its inner radius to hollow hemisphere in which the outer radius of the hollow hemisphere is thrice its inner radius.

Write the quadrants in which the following points lie:

$\left(-4,7\right)$