A student s average (arithmetic mean) test score on 4 tests is 68. What must be the student s score on a 5th test for the student s average score on the 5 tests to be 70?
70
72
74
76
78
Explanation:
This question is about averages. Typically, average questions are made easier by working with the sums, using the twist on the average equation:
Sum of the items = (average of items) (number of items).
From the first 4 tests, we have
Sum of the items = (68) (4)=240+32 = 272.
Using this equation again separately, if the fifth test gives an overall average of 70, then
Sum of 5 items = (70) (5) = 350
The difference of the sums is 350-272=78, so that would have to be the fifth test score to meet the condition stated by the question. The correct answer is (E).
This question is about averages. Typically, average questions are made easier by working with the sums, using the twist on the average equation:
Sum of the items = (average of items) (number of items).
From the first 4 tests, we have
Sum of the items = (68) (4)=240+32 = 272.
Using this equation again separately, if the fifth test gives an overall average of 70, then
Sum of 5 items = (70) (5) = 350
The difference of the sums is 350-272=78, so that would have to be the fifth test score to meet the condition stated by the question. The correct answer is (E).
