SOLUTION: Joseph does the laundry in 15 minutes. Mark takes 4 minutes more to do the laundry on his own than when he does it with Joseph. How long does it take when Mark and Joseph do the la

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Question 1006274: Joseph does the laundry in 15 minutes. Mark takes 4 minutes more to do the laundry on his own than when he does it with Joseph. How long does it take when Mark and Joseph do the laundry together?
(I don't know where to start! - thank you!)
Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!

Joseph does the laundry in 15 minutes. Mark takes 4 minutes more to do the laundry on his own than when he does it with Joseph. How long does it take when Mark and Joseph do the laundry together?
(I don't know where to start! - thank you!)
Let time it takes both, be B

Then both can do  of laundry in 1 minute 

Mark can do laundry in B + 4 minutes, or  of laundry in 1 minute

Joseph can do laundry in 15 minutes, or  of laundry in 1 minute

We then get: 

15B + B(B + 4) = 15(B + 4) ------ Multiplying by LCD, 15B(B + 4)









(B - 6)(B + 10) = 0 

B, or both can do laundry in:  minutes	   OR	         B = - 10 (ignore) 

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