2005 AMC 12A Problem 5

Attempt Problem 5 of the 2005 AMC 12A below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2005 AMC 12A solutions, or check the answer key.

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5.

The average (mean) of 2020 numbers is 30,30, and the average of 3030 other numbers is 20.20. What is the average of all 5050 numbers?

2323

2424

2525

2626

2727

Answer: B
Concepts:mean
Difficulty rating: 1020
Solution:

The total of all 5050 numbers is 2030+302020 \cdot 30 + 30 \cdot 20 =600+600= 600 + 600 =1200.= 1200.

The average is 1200÷50=24.1200 \div 50 = 24.

Thus, the correct answer is B.

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