Question

The average of three numbers is 94. The average of four different numbers is 87. What is the weighted mean of all the numbers together?

Answer 1

There are 7 numbers in total. 3 of them make up the average of 94, meaning that when you put all the numbers together, the 94 counts only 34% (from 3/7) towards the final mean. Likewise, 87 counts towards, 57% which is from 4/7. When calculating weighted averages, you do the sum of the averages, times the percentage of its weight.
\[\sum x _{i} w _{i}\]Where x is the average and w is the weight in percentages.
http://en.wikipedia.org/wiki/Weighted_mean#Convex_combination



Here's the work:

3/7 = 43% for the average of 94
4/7 = 54% for the average of 87

94(.43) + 87(.54) = 90.01

So, the weighted mean of all the numbers is about 90.



Also, next time you might want to post in the Mathematics section.
http://openstudy.com/study#/groups/Mathematics

Answer 2

thank you very muchooooo(:

Answer 3

No problem.