Find a missing number when you know the mean
Use the mean to find the total, then take away the numbers you know.
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The mean of 3 numbers is 5. Here are 2 of them: 6, 4. What is the missing number?
Answer: 5
The mean of 3 numbers is 5. Here are 2 of them: 4, 7. What is the missing number?
Answer: 4
The mean of 3 numbers is 10. Here are 2 of them: 6, 14. What is the missing number?
Answer: 10
Tip: Use the mean to find the total, then take away the numbers you know.
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