AVERAGE (Primitive Spread Function) returns the average of the specified values. 
SYNTAX: 
AVERAGE(value1,value2, ...)
REMARKS:
Accepts up to 30 arguments. Each argument can be a cell range, a float value, or an integer value. 
EXAMPLES:
AVERAGE(A1,B3,D5,E9)
AVERAGE(A1:A9)
AVERAGE(98,72,85)=85...