How quickly can the job be completed?

Question

Alex and Jake want to go hunting together, but first an important job must be completed. If Alex completed the job alone, it would take 4 hours. Jake has more experience and could complete the job by himself in 3 hours, If they worked together how quickly can the job be completed?

Answer 1

In one hour Alex does 1/4 of the job.

In one hour Jake does 1/3 of the job.

 

Together they complete the 1 job in x hours.

In x hours Alex does x/4 of the job.

In x hours Jake does x/3 of the job.

 

x/4 + x/3 = 1

3x + 4x = 12

7x = 12

x = 12/7

 

Working together they complete the job in one hour forty-three minutes.