To calculate the gradient we can use the equation for it, which is:
change in field value / distance = gradient
Since we already know the values, we can directly go with the calculation. The change in field value is 55 m - 15 m = 40 m, and we will need to convert the 20 km into meters, so we will have 20,000 m.
40 / 20,000 = 0.002
So the gradient of the suggest slope will be only symbolic 0.002 degrees.
