sandy wrote:

A standard machine fills paint cans at a rate of 1 gallon every 4 minutes. A deluxe machine fills gallons of paint at twice the rate of a standard machine. How many hours will it take a standard machine and a deluxe machine, working together, to fill 135 gallons of paint?

(A) 1

(B) 1.5

(C) 2

(D) 2.5

(E) 3

Here ,

The standard machine rate = \(\frac{1}{4} *60 minutes = 15 gallons/ hr\)

The deluxe machine rate = \(2 * standard machine rate = 30 gallons/hr\)

Therefore working together they fills = \(15 + 30 = 45 gallons/hr\)

Now to fill 135 gallons of paint

We know \(Work = Rate * Time\)

or \(135 = 45 * time\)

or \(time = \frac{135}{45} = 3 hr\)

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