rory has 180 pumpkins to sell.
1/4 of the pumpkins are lumina pumpkins
1/6 of the pumpkins are jack o'little pumpkin
1/10 of the pumpkins are sugar pie pumpkins
the rest of the pumpkins are cotton candy pumpkins
how many pumpkins are cotton candy pumpkins?
To find the number of cotton candy pumpkins, we need to subtract the sum of the other three types of pumpkins from the total number of pumpkins.
1/4 of the pumpkins are lumina pumpkins, which is (1/4) * 180 = 45 pumpkins.
1/6 of the pumpkins are jack o'little pumpkins, which is (1/6) * 180 = 30 pumpkins.
1/10 of the pumpkins are sugar pie pumpkins, which is (1/10) * 180 = 18 pumpkins.
The sum of lumina, jack o'little, and sugar pie pumpkins is 45 + 30 + 18 = 93 pumpkins.
So, the number of cotton candy pumpkins is 180 - 93 = 87 pumpkins. Answer: \boxed{87}.