Problem Solving 1.) The mean age of a group of 8 walkers is 42. Joanne joins the group and the
means now 40.
How old is Joanne?

Joel's and Mario's average speed is 19 kilometers per hour because it took them 1 hour to get from the campgrounds to the lake, which the speed can be found by v=d/t, in which v is velocity, d is distance, and t is for time. And the fact that it took them 2 hours, their speed is constant at the rate of 19 kilometers per hour because a round trip is from the campgrounds to the lake, which is 19 kilometers, and from the lake back to the campgrounds, which is another 19 kilometers.