Justin earned scores of 85, 92, and 95 on his science tests. What does he required to earn on his further science test to have an average (arithmetic mean) of 93%?
To earn an average of 93% on four tests, the sum of those four tests must be (93)(4) or 372. The sum of the first three tests is 85 + 92 + 95 = 272. The difference among the required sum of four tests and the sum of the first three tests is 100. He requires a 100 to earn a 93 average.