This applet is a graphical workbench for the exploration of upstream-downstream problems.[br]The representation is in the speed vs. time plane.[br][br]Explore the solution to the following problem -[br]An airplane can fly 3000 miles in 6 hours if there is no wind.[br]It can fly that distance in 7.5 hours when it flies against the wind.[br]It can fly that distance in 5 hours when it flies with the wind.[br][br]How fast does the wind blow?