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Two persons work together at the local aquarium. It takes the first person 120 minutes to clean the jellyfish tanks. Since the second person is new to the​ job, it takes him longer to perform the same task. When working​ together, they can perform the task in 70 minutes. How long does it take the second person to do the task by​ himself?

 Feb 24, 2020
 #1
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1st person rate   =    1 tank / 120 m

2nd person rate   =   1 tank / x m

 

 

1 tank /  ( 1 tank/120m + 1tank/xm)   = 70 m

 

1 / (1/120 + 1/x)  = 70

1 = 70 ( 1/120 + 1/x)  

1 - 70/120   = 70/x

x= 168 m

 Feb 24, 2020
 #2
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+1

S = second person

 

1 /70  -  1 / 120 = 1/S, solve for S

S = 168 minutes to clean the jellyfish tank.

 Feb 24, 2020

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