If it takes 5 machines 12 hours to complete a production run, how long would 3 machines take running at the same rate?

Correct answer to question 162 (Arithmetic Reasoning): 20 hours

Method

Fewer machines take longer, so multiply machines by hours to get the constant total work: 5 x 12 = 60 machine-hours. Dividing by 3 machines gives 20 hours.