Question

A person can do a job in 6 days. Another can do the same job in 4 days. If they work together, how long do they need to finish the job?

Answer 1

2.4 days

Explanation:

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Answer 2

2.4 days

Explanation:

Time working together,t ,is

1/t = 1/a+ 1/b where a and b is the times working alone

1/t = 1/4 + 1/6

Multiply each side by 12t to clear the fractions

12t( 1/t )= 12t(1/4 + 1/6)

12 = 3t+2t

12 = 5t

Divide by 5

12/5 = 5t/5

2 2/5 =t

2.4 days