Question 1205973
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Let's say the driveway is 170 square feet in area.
Feel free to pick any other positive real number. 
It turns out the driveway area doesn't affect the final answer.


If Leon takes 17 hours to do the job by himself, then his unit rate is 170/17 = 10 square feet per hour.
The formula is: unit rate = (amount done)/time


Assuming neither worker hinders the other, the two men work together at a combined rate of 170/5 = 34 square feet per hour.


Michael's unit rate when working alone is 34-10 = 24 square feet per hour.
This is because each person's unit rate combine together to get 34 square feet per hour.


So Michael will take 170/24 = 85/12 = 7 & 1/12 hours if he works alone.
The formula here is:  time = (amount done)/(unit rate)


That mixed number 7 & 1/12 hours is a bit clunky in my opinion. 
Let's convert to hours+minutes format.
1 hour = 60 min
1/12 of an hour = 60*(1/12) = 5 minutes
So 7 & 1/12 hour = <font color=red>7 hours + 5 minutes</font>


Or if you wanted purely minutes,
1 hour = 60 min
7 hours = 7*60 = 420 min
7 hours + 5 min = 420 min + 5 min = 425 min
Note that 425/60 = 85/12
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