The mean score is obtain by (sum of scores) ÷ (how many scores there are)
Class A:
Sum of scores = 60 + 68 + 70 + 75 + 84 + 86 + 90 + 91 + 92 + 94 + 94 + 96 + 100 + 100 = 1200
There are 14 scores in total
Mean scores of class A = 1200÷14 = 85.7
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Sum of scores of class B = 60 + 60 + 70 + 71 + 73 + 73 + 75 + 76 + 77 + 84 + 85 + 86 + 91 + 92 = 1073
Number of scores of class B = 14
Mean scores of class B = 1073÷14 = 76.6
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Class A has the highest mean score