Name: amy
Here is some help on a couple of your problems. Problem 1. Draw a diagram. Let x mph be the speed of the southbound train then the speed of the northbound train is x + 20 mph. In the first 4 hours after noon the northbound train goes 4(x + 20) miles. In the next hour it goes a further x + 20 miles and the southbound train goes x miles. From the diagram the distance between the trains at 5:00 pm is (x + 20) + 4(x + 20) + x miles. Set this equal to 160 miles and solve for x. Problem 2 Suppose that the sum of Clark's scores on the 15 weekly tests is x. If the weight of each of the 15 weekly tests is 1 and the average is 91 then x/15 = 91. Thus x = 15(91) = 1365. If his score on the final exam is F, its weight is 5 and the overall weighted average is the sum of the weighted scores divided by the sum of the weights. That is (1365 + 5F)/(15 + 5). But this is 85 so solve (1365 + 5F)/(15 + 5) = 85 for F. Cheers,Penny
