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Question

The Green family and the Wilson family each used their sprinklers last summer. The water output rate for the Green family's sprinkler was 25L

 per hour. The water output rate for the Wilson family's sprinkler was 20L

 per hour. The families used their sprinklers for a combined total of 55

 hours, resulting in a total water output of 1250L

. How long was each sprinkler used?

Answer 1

The amount of water used = rate used multiplied by the time used.

Let "G" be the time the Green family used their sprinkler. Since the total time for both families is 55 hours, we can say the Wilson family used their sprinklers for "55 - G".

The amount of water the Greens used is their rate multiplied by their time: 25G

The amount of water the Wilsons used is their rate multiplied by their time: 20(55 - G)

So their combined water usage was 25G + 20(55 - G) and that equaled 1250

25G + 20(55 - G) = 1250

25G + 1100 - 20G = 1250

5G = 150

G = 30

Wilson's time was 55 - 30 = 25

Answer 2

System of equations with two unknowns. We need two separate formulas.

Easy one first (total hours)

G + W = 55

harder one second ( total water usage)

25G + 20W = 1250

Algebra time: (elimination)

25G + 20W = 1250

20G + 20W = 1100 <- multiplied formula 1 by 20

Subtract and 5G = 150 G= 30

Plug G back in to formula one and W = 25