



 
Hi Rebecca, First let's get the time units constant. I'm going to choose seconds. There are 60 seconds in a minute so The circumference of a circle is 2 π times the radius so if the radius of the circle is r feet then its circumference is
The pulley moves 10/3 revolutions in a second so that's 2 πr × 10/3 feet in a second. But you are told that the belt, which runs on the pulley, moves at 30 feet in a second. Thus
Solve for r. Penny  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 