Multiple choice

Average of 17 students in a class is X. When their marks are arranged in ascending order it was found to be in Arithmetic Progression. The class teacher found that the students who ranked 15th, 11th, 9th and 7th had copied the exam and hence they are suspended. Now the average of the remaining class is Y. Then

  1. X = Y

  2. X > Y

  3. X < Y

  4. X = 2Y

  5. Data is not sufficient
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

17 students in AP. Average X = middle term (9th term) = a + 8d. Removing ranks 7, 9, 11, 15 removes values above average (these are later terms in AP). When you remove values above average from a set, the new average Y decreases. Example: AP 1,2,3,...,17 has avg 9. Remove 7,9,11,15 and new avg becomes 8. So X > Y.

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