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SAT Math Practice Exam

Category - Mathematics - Hard

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The average(arithmetic mean) of eight numbers is 12.5. When one number is discarded, the average of remaining numbers becomes 12.0. What is the discarded number?
  1. 10.5
  2. 12.0
  3. 12.5
  4. 16.0
Explanation
Answer D The average of eight numbers is 12.5. Total of 8 numbers = 12.5 X 8 = 100
Average of 7 numbered is 12 . Total of 7 number = 12 x 7 = 84
Hence the eighth number = 100-84 = 16


Key takeaway: GMAT always refers to an average as average (arithmetic mean) The average ( arithmetic mean ) of a set of numbers is their sum divided by the number of numbers in the set. For average problems, think Total divided by number of items.
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