 
 <translate> A pipe can fill a cistern in 18 minutes whereas the cistern when fill can be emptied by a leak in 20 minutes. When both pipes are opened, find when the cistern will be full?
Options:
(A) 17
(B) 180
(C) 70
(D) 120
(E) 12 Now, let's think a bit. Some random thoughts: <ibo> Otu ọkpọkọ nwere ike imejupụta olulu mmiri n'ime nkeji iri na asatọ ebe olulu mmiri ahụ nwere ike ịgbapụta mmiri n'ime nkeji iri abụọ. Mgbe e meghere paịpụ abụọ ahụ, chọpụta mgbe olulu mmiri ahụ ga-ejupụta? Nhọrọ: (A) 17 (B) 180 (C) 70 (D) 120 (E) 12 Ugbu a, ka anyị chee echiche. Ụfọdụ echiche na-enweghị isi: 