Here is a graphical workbench that lets you explore a problem that many students have difficulty with:[br][br][br]Joe can paint a wall by himself in four hours.[br][br]Sam can paint the same wall by himself in two hours.[br][br]How long will it take them to paint the wall if they work together?[br][br][br]The graphical representation is in the walls/hr - hours plane[br][br][br]CHALLENGE –[br]a. Use this app to pose and solve a different problem – Joe and Sam can each paint the wall alone in 3 hours.[br][br]b. Use this app to pose and solve a different problem –[br][br] Joe can paint the wall alone in 2 hours, and together Joe and Sam can paint the wall in one hour.[br][br] How long would it take Sam to paint the wall if he were painting by himself?[br][br]c. Make up a new problem like this in which Joe paints 3 times as fast as Sam.[br][br]d. Make up and solve a problem in which Joe, Sam and Mary all work on painting the wall.