The girls want to have streamers of ribbons hanging from the entrance door. they plan to put 11 six foot long ribbons on the door. The ribbons comes in 24-foot long rolls. how many rolls do they need?

There need to be three rolls, but there's gonna be extras

You can get 4 - 6ft long rolls out of one 24ft long roll

two 24ft long rolls will produce 8 - 6ft long rolls

and three 24ft long rolls will produce 12 - 6ft long rolls

so the girls will need three 24ft long rolls for their purpose (note: they will be left with one extra 6ft long roll)