Give the step-by-step reasoning process and then the final answer. Jacob takes four tests in his physics class and earns 85, 79, 92 and 84. What must he earn on his fifth and final test to have an overall average of 85?
Since wants needs an 85 as an average and he takes five tests, he must have 85 * 5 = 425 total points. Currently he has 85 + 79 + 92 + 84 = 340 points. So for his fifth test he needs 425 - 340 = 85 points.
The final answer: 85.