Average Circles

[shyra1353]

While studying for my SATs, I came across a couple of questions that required you to use average circles to answer them. I have never heard of an average circle, and neither have the people I have asked. I ran a search on google, but didn't find anything remotely useful. So here is my question, what is an average circle, when and how do you use it, and is there a simpler way ??

For those of you wondering, the original question is:
The average (arithmetic mean) of the weight (in pounds) of a kennel of v dogs is 40, and the average weight (in pounds) of a kennel of w dogs is 64. When the weights of both kennels are combined, the average is 54. What is the value of (v/w)?
If anyone is interested, I will post the correct answer later ...

And for the record, an average circle is NOT a circle that is not too big and not too small, but is just right .. lol ...