Kim earned scores of 87, 83 and 88 on her first three mathematics examinations. If Kim receives a score of 90 on the fourth exam, then by how much will her average increase?
I want to compare Kim's average score before and after the fourth exam. To find her average before the fourth exam, I need to add up her first three scores and divide by three. That is, 87 + 83 + 88 = 258, and 258 / 3 = 86. So her average before the fourth exam is 86. To find her average after the fourth exam, I need to add up all four scores and divide by four. That is, 87 + 83 + 88 + 90 = 348, and 348 / 4 = 87. So her average after the fourth exam is 87. The difference between the two averages is how much her average will increase. That is, 87 - 86 = 1. So her average will increase by 1 point. 