If the frequency of q of a trait is 0.4, what is the frequency of p?

In genetic traits, p and q represent the relative probabilities of the two alleles manifesting. If these two are the only options (ex. a dominant one and a recessive one), then the probabilities of both must sum up to 1. In this case, since we are given that q = 0.4, then p + q = 1, p + 0.4 = 1, and p = 0.6.

P = 0.6 ...