A small factory with 3 machines has a job of stamping out a number of pan covers. The newest machine can do the job is 3 days, another machine can do it in 4 days, and the third machine can do it in 6 days. How many days will the factory take to do the job using all the machine?

Correct Answer: 1.333
First machine can finish stamping out 1/3 of the pan covers in 1 day Second machine can finish stamping out 1/4 of the pan covers in 1 day Third machine can finish stamping out 1/6 of the pan covers in 1 day Together they can finish (1/3 + 1/4 + 1/6 = ) 9/12 = 3/4 of the pan covers in 1 day. So, they can finish stamping all of the pan covers in 3/4 = 1.33 days