According to the Hardy-Weinberg principle:
Frequency of dominant allele (A) = p =0.4
Frequency of recessive allele (a) = q
Sum total of all the allelic frequencies is 1, i.e. p+q = 1
⇒ 0.4 + q = 1
⇒ q = 0.6
Frequency of AA individuals = p × p = p2 = (0.4)2 = 0.16
Frequency of aa individuals = q × q = q2 = (0.6)2 = 0.36
Frequency of Aa individuals = 2pq = 2(0.4)(0.6) = 0.48