12 1/2 gallons would provide one large (16 oz.) glass for everybody. If you put ice cubes in the glass and the tea is not iced, I would think that 8 gallons might do it, so 12 gallons would allow seconds for many. Tea is relatively cheap- be sure to make plenty. You can make it very strong and dilute it as you need it.
100 litres = 26.4172052358 gallons
106
100 US gallons is 378,540 mL
100 liters = 26.42 US gallons.
100 US gallons is about 378.541 liters.
400
100 gallons is 1/2 cubic yard.
There are 748 gallons in 100 cu ft.
About 4 gallons, allowing for an 8 oz. serving, One gallon will serve about 16 people.
0.03 gallons.
100 gallons is 12,800 fluid ounces.
There are approximately 22.01 imperial gallons in 100 liters.