question: Sally received the following scores on her math quizzes: 50, 80, 80, 60, 40, 90, 100, 70, and 60. Find her mean score.
answer: Sally's total score is 50 + 80 + 80 + 60 + 40 + 90 + 100 + 70 + 60 = <<50+80+80+60+40+90+100+70+60=630>>630.
  Her mean score is 630 / 9/quizzes = <<630/9=70>>70/quiz.
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