2005 AMC 12A Problems/Problem 5
Contents
[hide]Problem
The average (mean) of 20 numbers is 30, and the average of 30 other numbers is 20. What is the average of all 50 numbers?
Solution
Solution 1
The sum of the first 20 numbers is and the sum of the other 30 numbers is . Hence the overall average is .
Solution 2
This is just the harmonic mean. Answer is .
Solution by franzliszt
See also
2005 AMC 12A (Problems • Answer Key • Resources) | |
Preceded by Problem 4 |
Followed by Problem 6 |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | |
All AMC 12 Problems and Solutions |
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