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About John Zalewski
Expertise
I can help you solve problems involving fractions, decimals, ratios, and algebra. I can teach you how to do math faster, and even in your head. I can teach math definitions, and help you study, if necessary. Please do not ask any graphing, trigonometry, or calculus questions. Try to work through homework questions before asking for assistance.

Experience
I routinely process numbers of all kinds in my head, without need of a calculator.

Education/Credentials
I was an A math student while in high school.

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Basic Math - Mathematics

Expert: John Zalewski - 9/26/2008

Question
The average of a group of 20 numbers is 20. The average of a different group of 60 numbers is 60. The two groups of numbers are combined into a single group. What is the average of the combined group?

Answer
Hello, Vernon.

The answer is 50.

If you have 20 numbers, and the average is 20, that means the total is 400 (400/20 = 20).

If you have 60 numbers, and the average is 60, the total is 3600 (3600/60 = 60).

Therefore, you have a grand total of 4000 (3600 + 400), and 80 numbers (60 + 20).

4000/80 = 50.

Regards,
John

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