I doubt all of them would want coleslaw, but plan on 1/2 cup for each person. That would be 35 cups of coleslaw, so the safe bet would be to have 2 gallons in case some come back for seconds.
About 2 gallons.
Three.
30
20
6 Pounds of coleslaw can feed around 45 - 50 people
I would use that for 4 people.
First we need to know how many of 100 people will eat it. Let's assume each person eats 1/2 cups. You'd make 50 cups = ~3 gallons. So around 3 gallons, in my opinion, would be enough. There will be people who eat none leaving extra for people who eat a lot. If you know the people coming aren't big fans, 1-2 gallons should be plenty.
Approximately 8 people
about 20 people give or take how hungry the people are
5 gallons
15000 gallons
About 7,570.824 mL is needed to equal two US gallons.
(100 people) x (8 oz per person) / (128 oz per gallon) = 6.25 gallons