houston1980
On a recent test taken by 21 students, each student’s test score was between 0 and 100, inclusive.
Was the average (arithmetic mean) of the 21 scores on the test greater than 75 ?
(1) The median of the 21 test scores was 80.
(2) The minimum of the 21 test scores was 70.
Given- The test was taken by 21 students
- Each student scored between 0 and 100, inclusive
Question Is the average of the 21 scores greater than 75 ?
If we arrange the scores in ascending order, the 11th score is the median score. We might not need this immediately, but its good to keep the information handy.
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Statement 1(1)The median of the 21 test scores was 80Case 1: Let's assume that all the students scored 80 on the test. In that case, the average score of 21 students will be 80.
Is the average of the 21 scores greater than 75 ? → Yes !
Case 2: Let's assume that 10 students scored 0 on the test and 11 students scored 80 on the test. In that case, the average will be around 40.
Is the average of the 21 scores greater than 75? → No !
As we are getting contradicting answers, the statement alone is not sufficient and we can eliminate A and D.
Statement 2(2)The minimum of the 21 test scores was 70Case 1: Let's assume that all the students scored 70 on the test. In that case, the average score of 21 students will be 70.
Is the average of the 21 scores greater than 75? → No!
Case 2: Let's assume that only one student scored 70 on the test and the rest 20 students scored 100 on the test. In that case, the average will be greater than 75.
Is the average of the 21 scores greater than 75? → Yes!
As we are getting contradicting answers, the statement alone is not sufficient and we can eliminate B.
CombinedFrom statement 2, we know that the minimum score on the test is 70. Hence to find the lowest possible average, let's assume that the 10 students scored a 70 on the test, and 11 students scored an 80 on the test.
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If that were the case, the average = \(\frac{(80*11)+(70*10)}{21} = \frac{1580}{21} = 75.XX\)
Hence, the minimum possible average is greater than 75.
The statements combined are sufficient.
Option C