Patrycia’s overall grade in her physics class is based solely on the average of her scores on 6 unit tests. The grade she received on the first 5 tests are as follows: 89, 93, 95, 92, 90. What grade does Patrycia need to earn on her 6th unit test to end up with a 90% in the class?

Question

Patrycia’s overall grade in her physics class is based solely on the average of  her scores on 6 unit tests. The grade she received on the first 5 tests are as follows: 89, 93, 95, 92, 90. What grade does Patrycia need to earn on her 6th unit test to end up with a 90% in the class?

texaschic101 · Answer

(89 + 93 + 95 + 92 + 90 + x)/6 = 90%
(459 + x)/6 = 90% (multiply by 6)
459 + x = 540
x = 540 - 459
x = 81

check...
(459 + 81)/6 = 90%
540/6 = 90%
90% = 90% (correct)

She would have to make an 81