The mean of four numbers is 7. Three of them are 5, 6 and 9. What is the fourth?
Answer and explanation
Correct answer: C.
- Step 1: The sum of four numbers with mean 7 is . Step 2. The three known numbers add to 20, so the fourth is . **Answer: . Why not the others:** 7 is the mean itself, and 9 and 6 do not make the sum 28.
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