SOLUTION: On 3 tests, Rajas had scores of 70, 72, and 80. What score must he get on the fourth test to raise his average test score by exactly five points? So, I'm kind of lost because it as

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: On 3 tests, Rajas had scores of 70, 72, and 80. What score must he get on the fourth test to raise his average test score by exactly five points? So, I'm kind of lost because it as      Log On


   

Question 1007084: On 3 tests, Rajas had scores of 70, 72, and 80. What score must he get on the fourth test to raise his average test score by exactly five points? So, I'm kind of lost because it asks to find it exactly 5 points higher.
Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
the average of the 3 scores is equal to (70 + 72 + 80) / 3 = 222 / 3 = 74

the total of the 3 scores is 222.
the average of the 3 scores is 74.

you want to raise the average by 5 points.
the new average will have to be 74 + 5 = 79
that new average is over 4 scores.

4 * 79 = 316
the total of the 4 scores needs to be 316 in order for the average of the 4 scores to be 79.

the total of the 4 scores minus the total of the 3 scores will be equal to the fourth score.

316 - 222 = 94

the fourth score will need to be 94 in order for the average of the 4 scores to be 79.

222 + 94 = 316
316 / 4 = 79
79 = 74 + 5