Problema Solution

Together it takes 

Ann 

and 

Dan 

1 

hr 

12 

min to sort recyclable materials. Alone, 

Ann 

would require 

1 

more 

hour 

than 

Dan. 

How long would it take 

Dan 

to do the job alone?

Answer provided by our tutors

let


x = the number of hours Dan needs to do the job alone, x>0


1/x job per hour is the rate of Dan


x + 1 = the number of hours Ann needs to do the job alone


1/(x + 1) job per hour is the rate of Ann


together they need 1 hr 12 min = 1 + 12/60 = 1.2 hr to finish the job


1/1.2 job per hour is the together rate


1/x + 1/(x + 1) = 1/1.2


by solving we find:


x = 2 hr


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Dan needs 2 hours to dp the job alone.