Question

Rosita can wax her car in 2 hours or 120 minutes. When she works together with Helga, they can wax the car in 45 minutes. How long would it take Helga, working by herself, to wax the car?

Answer 1

Time taken by Helga to wax the car is 72 minutes

Step-by-step explanation:

Let w be the work of waxing.

Rosita can wax her car in 2 hours or 120 minutes.

Time taken by Rosita = 120 minutes

$\texttt{Rate of Rosita = }\frac{W}{120}$

Let time taken by Helga be t,

$\texttt{Rate of Helga = }\frac{W}{t}$

When she works together with Helga, they can wax the car in 45 minutes.

We have

             $\frac{W}{\frac{W}{120}+\frac{W}{t}}=45\\\\120t=45(120+t)\\\\120t=5400+45t\\\\t=72minutes$

Time taken by Helga to wax the car is 72 minutes