math word problem

Question

Susan can wax her car in 2 hr(s). When she works together with Helga, they can wax the car in 30 minute(s). How long would it take Helga, working by herself, to wax the car?

Answer 1

If you add units to this equation it will make a lot more sense.

And the solution gives an answer of x=2/3, but 2/3's what?  day, hour, min

 

Susan is 1 car per 2 hours

Helga is 1 car per x.

Together 1 car per 2 hours + 1 car per x = 1 car per (1/2)hour

then 1 car / 2 hours + 1 car / x = 1 car / (1/2) hour = 2 cars / hour

       1 car / x = 2 cars / hour - 1 car / 2 hours

                     = 4 cars / 2 hour - 1 car / 2 hours    

                    = 3 cars / 2 hour

So  1 car / x = 3/2 cars/hour

Therefor  x = 2/3 hours / car

Answer 2

To set up this equation, Susan is 1/2 and Helga is 1/x. Together 1/2 + 1/x = 1/(1/2) = 2. Then 1/x=3/2 and x= 2/3. Hope that helps!

 

Deanna