for 2 numbers, x and y, the average is

A=(x+y)/2

for n numbers, the average is

A=(x1+x2+x3+.....+xn)/n

There is a number that shows the rise and fall. This is the tangent . For example:

Temperature 1: 25 degrees C measured at 1:00 (time)

Temperature 2: 27 degrees C measured at 2:00 (time)

The tangent (slope) is

T= (Y2-Y1)/(X2-X1) = (2-1)/(27-25)

This tangent is a number that shows the degrees of rising and falling (in rads). Using arctangent you can get this number in degrees.