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CEMC Gauss (Grade 7), 2016

Algebra Difficulty 1.6 Junior Find the answer Canada

The mean (average) of a set of six numbers is 10. When the number 25 is removed from the set, the mean of the remaining numbers is

Pick one

Solution

The mean (average) of the set of six numbers is 10, and so the sum of the set of six numbers is $6\times10=60$ .

If the number 25 is removed from the set, the sum of the set of the remaining five numbers is $60-25=35$ .

The mean (average) of the remaining set of five numbers is $35\div5=7$ .

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