Help in Hardy-Weinberg - (Nov/10/2010 )

I have trouble understanding this question and I dont know how to solve this step by step. Can anyone help me? Thanks

If 9% of an African country's population is born with a severe form of sickle-cell anemia (ss), what percentage of the population will be more resistant to malaria because they are heterozygous (Ss) for the sickle-cell gene?

p2+2pq+q2 - sorry for the formatting, you know this equation, right?
p= dominant allele
q= recessive allele

q+p=1

you know that q2 = 0.09 in this case
so, square root of q2 = 0.3

using q+p=1,
0.3+p=1
1-0.3=p
p=0.7

p2+2pq+q2
0.7 2 + 2 * 0.6* 0.7 + 0.09

therefore, Ss = 2*0.6*0.7 = 0.42
0.42 = 42%

sorry for the formatting, but do you follow?