In a population of gerbils, long hair (h) is completely dominant over short hair (h). if 18% of the population has short hair, calculate the percentage of the population that is expected to be heterozygous (hh).

Below are the choices that can be found elsewhere:

A) 29% 
B) 58% 
C) 80% 
D) 49%

q^2 + 2pq + p^2=1 

And q + p = 1 

You have q^2 which is 0.18, which stands for the homozygous recessive. p^2 is homozygous dominant percentage while 2pq is what you're looking for, heterozygous. 

Anyway to find your answer, square root q^2 to find q, then you can use q+p=1 to find p. Then use 2pq to find the percent of heterozygotes. The answer for your question is D.