Find the missing measurement round answer to nearest tenth

Anewborn baby had about 26,000,000,000 cells. an adult has about 4.94 times 10 to the 13 power cells. how many times as many cells does an adult have than a newborn

Dawn is selling her mp3 player for 3 4 of the original price. the original price for the mp3 player was $40. how much is she selling her mp3 player for?

Sara goes on a slingshot ride in an amusement park. she is strapped into a spherical ball that has a radius 3*10^2 of centimeters. what is the volume of air in the spherical ball? use this formula: volume of a sphere=4/3pi, r^3 , where r is the sphere’s radius.