On a certain river a paddle boat travels 8 miles upstream (against the current) in the same amount of time and travel 16 miles downstream (with the current). if the current of the river is 4 mph determine the speed of the boat in still water.

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.