Change size of several objects but lock their position?

I've had this time consuming problem many times:
For instance, I have several circles scattered over my work space, all the same size. Then I decide that they are a little too big or small. I want to adjust their size, but I have to do it one by one because I want them to stay in their position.
Is there a way of changing their size all at once, but keeping them in place? 

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