Question

A and B do a job together in two hours. if A completes the job alone in 5 hours, how long will it take B to complete the job?

Answer 1

Step-by-step explanation:

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Answer 2

Answer:

3 hours 20 mins

Step-by-step explanation:

A and B can do the job in 2 hours

⇒ 1 hour = 1/2 of the job

A can complete the job alone in 5 hours

⇒ 1 hour = 1/5 of the job

Assumed B can complete the job alone in x hours

⇒ 1 hour = 1/x of the job

Solve x:

1/x + 1/5 = 1/2

(5 + x)/5x = 1/2

2(5 + x) = 5x

10 + 2x = 5x

3x = 10

x = 10/3 hours

Therefore,

B takes 10/3 hours to complete the job.

Convert 10/3 hours into hours and mins

10/3 hours = 3 1/3 hours

10/3 hours = 3 hours 1/3 x 60 mins

10/3 hours = 3 hours 20 mins

Answer: B will take 3 hours 20 mins to complete the job.