What is the impact of the number of coils on the spring rate of extension springs, compression springs or torsion springs?

The number of coils counts one by one in the denominator of the formula of the spring rate of extension and compression springs. When the number of coils increase by 10%, the denominator in the formula increases by 10% and the formula lower and the spring rate thus decreases by almost 10%.

The same calculation can be used for torsion springs.