Practice Quiz

SAT Math Practice Exam

Category - Mathematics - Hard

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In an examination of 4 subjects, John gets 100, 60 and 55 in three subjects. If his average (arithmetic mean) marks for all four subjects is 75, then the marks in the 4th subject must be
  1. 82
  2. 85
  3. 88
  4. 91
  5. 93
Explanation
Answer B The average marks for all four subjects is 75 and so total marks are 4 x 75 = 300
The marks for three subjects are given and their total is 100 +60 + 55 = 215. Hence the marks for the fourth subject = 300- 215 = 85

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