this page seems like a good, simple explanation and was the first hit on Google for search: grouped mean.
First of all, a little background. The problem gave me 37 numbers, from which I created a grouped frequency distribution table. Based on the table, I then created a histogram.
Now I don't understand the third part of the question: "(d) Find the grouped mean of these data from the classes used in (a)."
How do I do this? Is this enough information, or do I need to give you the specifics?