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2021 AMC Fall 10A Problem 10

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2021 AMC Fall 10A Problem 10AMC 10 Step by Step
Name:                             Date: September 13, 2026
Statistics & Data · difficulty 2 of 5 · about 3 min · position P1-10

A school has 100100 students and 55 teachers. In the first period, each student is taking one class, and each teacher is teaching one class. The enrollments in the classes are 50,20,20,5,50, 20, 20, 5, and 55 . Let tt be the average value obtained if a teacher is picked at random and the number of students in their class is noted. Let ss be the average value obtained if a student was picked at random and the number of students in their class, including the student, is noted. What is t−st-s ?

  1. A)

    −18.5{-}18.5

  2. B)

    −13.5{-}13.5

  3. C)

    00

  4. D)

    13.513.5

  5. E)

    18.518.5

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