In guinea pigs, short hair (S) is completely dominant to long hair (s). If a long-haired guinea pig is

crossed with a homozygous dominant guinea pig what percentage of their offspring will be long-haired and short-haired?

Square is 2x2

3 answers

If a long-haired guinea pig (ss) is crossed with a homozygous dominant guinea pig (SS), their offspring will all be heterozygous short-haired (Ss).

Therefore, 100% of the offspring will be short-haired.
Make the punnet square for it
Sure, here is the Punnett square for the cross between a long-haired guinea pig (ss) and a homozygous dominant guinea pig (SS):

S S
s Ss Ss
s Ss Ss

As you can see, all the offspring will be heterozygous short-haired (Ss), so 100% of the offspring will be short-haired.