SUPPOSE THE RADIUS OF PLANET E IS 6.4*10 TO THE POWER OF 3 KM AND THE RADIUS OF PLANET M IS 3.2*10 TO THE POWER OF 3 KM AND SEAS COVER THREE QUARTERS OF THE

Question

SURFACE E , BUT M's SURFACE IS ALL DRY LAND . WHAT IS THE RATIO OF THE LAND SURFACE AREA OF PLANET E TO THE LAND SURFACE AREA OF PLANET M ?

Answer 1

The formula for the surface area, S, of a sphere is:

 

S = 4(pi)r²

 

So the surface areas of the two planets, E and M are:

 

S_E = 4(pi)r_E²

S_M = 4(pi)r_M²

 

Where r_E and r_M are the radii of the two planets (given in the problem statement).  3/4 of the surface area of planet E is covered with seas, so only 1/4 is covered with land.  All of planet M is covered with land.  The ratio of the dry land areas of planets E to M is:

 

(1/4)S_E/S_M = S_E/4S_M = (4(pi)r_E²)/4(4(pi)r_M²) = r_E²/4r_M²

 

Plug in the radii of planets E and M (r_E and r_M) to get the answer.