SOLUTION: Could someone please help me with this problem? The average of the first three numbers was 42. The average of the next seven numbers was only 12. What was the average of all the nu

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Question 570535: Could someone please help me with this problem? The average of the first three numbers was 42. The average of the next seven numbers was only 12. What was the average of all the numbers?
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Let's say that the first three numbers are: a, b, and c. We need to find their sum.
%28a%2Bb%2Bc%29%2F3+=+42 "The average of the first three numbers was 42".
So the sum of the first three numbers is 3%2842%29+=+126
The next seven numbers we'll identify as: d, e, f, g, h, i, j and their average is:
%28d%2Be%2Bf%2Bg%2Bh%2Bi%2Bj%29%2F7+=+12 "The average of the next seven numbers was only 12". So their sum is 7%2812%29+=+84
So we have 10 numbers altogether. To find their average, divide their sum by the number of numbers (that's 10):
%28126%2B84%29%2F10+=+210%2F10=21
The average of all ten numbers is 21.