In the book Door in the Wall we discussed the distance (how far) Robin traveled, the rate of speed (how fast) he traveled at, and the amount of time (how long) it took him to finish. Any of these variables can be determined using the formula, distance equals rate multiplied by time (d = r x t), as long as we have two of the three variables. For the examples given on this page, find the missing variable using the formula, show all of your work.