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JEE Main202228 Jun 2022Evening ShiftMathematicsStatisticsActual

Suppose a class has 7 students. The average marks of these students in the mathematics examination is 62 , and their variance is 20 . A student fails in the examination if he/she gets less than 50 marks, then in worst case, the number of students can fail is

Correct answer

0

Step-by-step solution

Applying the formula of variance we get, 20 = ∑ i = 1 7 x i - 62 2 7 ⇒ x 1 - 62 2 + x 2 - 62 2 + … . + x 7 - 62 2 = 140 If x 1 = 49 (taking the least possibility) 49 - 62 2 = 169 then, x 2 - 62 2 + … . + x 7 - 62 2 = 140 - 169 = - 29 Negative Number which is not possible, therefore, no student can fail.

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