George scored an average of 80% on three tests. What score must he get on the fourth test to bring his average to 85%?
a.85%
b.88%
c.90%
d.95%
e.100%

Question

George scored an average of 80% on three tests. What score must he get on the fourth  test to bring his average to 85%?
a.85%
b.88%
c.90%
d.95%
e.100%

anonymous · Answer

After his next test, his average score will be the total of his last 3 scores, "240", plus his next test score, "nts", divided by the number of tests he will have taken, "4". This may be expressed this way:

average score after next test = (240+nts)\4

If he needs that average score to be 85, then he has to solve for "nts" in this equation:

85 = (240+nts)\4