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.