How many robots are needed if 300 chairs have to be built from 2:00 p.m. to 7:00 p.m. by a team of robots if each takes 4 minutes to build one...

First, lets see how much time the robots total took. Since
the rate of robots is measured in minutes, lets changed the number of hours into
minutes.

7-2 = 5 HOURS= 5*60= 300
minutes

so every robot worked 300
minutes.

Let's see how many chairs can one robot build in
300 minutes

300/4 = 75
chairs

the total robot team built 300
chairs.

Inevitably, there are 300/75 = 4 robots in the
team

The final answer to this MC is D (4
robots).

Actually, this could be solved by
plugging in method. However, i prefer to use algebra.