设这批面粉有X袋
(X-1/4X-110):1/4X=4:5
1/4X×4=5×(X-1/4X-110)
X=5×(3/4X-110)
X=15/4X-550
15/4X-X=550
11/4X=550
X=550÷11/4
X=200