Average Account Activities Report:

Average Account Activities Report:
Report types in salesforce gives flexibility to create custom reports with or without related records for standard and custom objects.The following example shows accounts with or without average activities .First step in this report create a formula field always one on account give value 1 .Second step create a custom report type on account with or without related activites.Finally create a summary report using report type and  create formulas on the report as show below.Make sure your custom field always one added in the custom report type.