Question

A chandelier has sockets for 12 light bulbs. Suppose there are 75 of these

Answer 1

-- First, we need to know how many total sockets there are in the auditorium.

(75 chandeliers) x (12 sockets/chandelier) = 900 sockets

-- Now, in order to fill 900 sockets, we'll need 900 bulbs.

(900 bulbs) / (4 bulbs/box) = 225 boxes

If all the bulbs we buy are good ones, and we don't drop any while we're installing them, then we can just exactly do the job with 225 boxes.