Approximately 70.8% of Earth’s surface is covered with water; the rest is land. It is said that Mars, whose surface is covered entirely with land, has approximately the same amount of land as the earth. Based on this information, what percent of Earth’s radius is Mars’ radius? Express your answer to the nearest whole number.
Surface Area of a sphere =4*pi*r^2
SA of Earth =4 * 3.141592 x 6,371^2 =5.1 * 10^8 km^2
5.1E8 * 29.2%[percentage of land on Earth] =148,938,826 km^2 -SA of Mars(approx.)
148,938,826 /[4*pi] =11,852,175 km^2 - Take the square root of this.
Sqrt(11,852,175) =~ 3,443 km (approx) -the radius of Mars.
3443 / 6371 [This is Earth's radius] =~54% of Earth's radius is Mars's radius.