The average of four numbers is 15. Three of the numbers are 12, 18 and 10. Find the fourth number.
A15
B25
C20CORRECT
D18
Common EntranceMathematicsAverage
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Why the answer is C, and why the others tempt you.
Total of four numbers = 4 x 15 = 60. 12 + 18 + 10 = 40, so the fourth number is 60 - 40 = 20.
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