Measure Quantity tool shows accumulated quantities of objects

Select Measure Quantity tool.
Hold Shift key and select multiple objects.
Observe total Surface Area and Volume of all selected objects in Tool Options palette.
To select a segment or face of an object hold down the Cmd key (Mac) or Ctrl key (Win).
To select multiple segments or faces hold Cmd + Shift keys (Mac) or Ctrl + Shift keys (Win).
Observe total Boundary Length or Surface Area of selected segments or faces.