Empty a Swimming Pool . . . With Only a Red Solo Cup
JavaScript ES6, 100 78 82 81 74 bytes

Thanks to @UndefinedFunction for helping golf off 4 bytes

(a,z,d,f=([a,g,k,p])=&gt;g*k*(a[6]?p/-~!a[8]:3.14*g))=&gt;Math.ceil(f(a)/f(z))*d


Usage:

t(["triangle",10,12.25,3],["circle",5,2.2],5);