This applet serves well to find how much paint work can be done when multiple people work together. There is one input time, which is a, and the speed of work is different for each person. To find how many walls can be painted, you just input time(a), and the rates (Ra, Rb, Rc). To find how long it takes to finish a job(like one wall or two walls) with given rates(Ra, Rb, Rc), you adjust the Total Walls to 1 or 2 and it will figure out how long it takes.
