phil takes 3 hours to do a job. his assistant, john, takes 4.5 hours for the same job. if john helps phil do the job for 1 hour, how long will it take phil to complete the job by himself?

Answer 1

(1 / 3) + (1 / 4.5) + (P / 3) = 1

3 + 2 + 3P = 9, multiply both sides by 9

3P = 4

P = 4 / 3

It take Phil 1 and 1/3 hours working alone.

Answer 2

In one hour Phil will complete 1/3 of the job.

In one hour John will complete 1/4.5 (simplified to 2/9) of the job.

Add these together to get the total amount of the job completed: 1/3 + 2/9 = 5/9

So we still have 4/9 of the job remaining. Phil working alone will take 4/9 * 3 hrs to complete the job.

Answer 4/3 hours, or 1 hour and 20 minutes