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 chair?

A. 19

B. 6

C. 5

D. 4

E. 3

### 2 Answers | Add Yours

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.

The chairs are to be built from 2:00 p.m. to 7:00 p.m. That is a time period of 5 hours or 5*60 = 300 minutes.

The number of chairs to be built is 300. This essentially means that 1 chair should be built in a minute.

As each robot takes 4 minutes to build a chair, 4 robots are required to be able to build 4 chairs in 4 minutes or 1 chair in 1 minute.

**The correct answer is option D or 4 robots.**

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