SOLUTION: The Thomas family and the Clark family each used their sprinklers last summer. The water output rate for the Thomas family's sprinkler was 35L per hour. The water output rate for t

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Question 951939: The Thomas family and the Clark family each used their sprinklers last summer. The water output rate for the Thomas family's sprinkler was 35L per hour. The water output rate for the Clark family's sprinkler was 15L per hour. The families used their sprinklers for a combined total of 40 hours, resulting in a total water output of 1100L. How long was each sprinkler used?
Thomas family sprinkler:
Clark family sprinkler:
Answer by macston(5194) About Me  (Show Source):
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T=Thomas usage; C=Clark usage
T+C=40hrs
T=40hrs-C
35L/hrT+15L/hrC=1100L Substitute for T
35L/hr(40hrs-C)+15L/hrC=1100L
1400L-35L/hrC+15L/hrC=1100L Subtract 1400L from each side.
-20L/hrC=-300L Divide each side by -20L/hr
C=15 hrs ANSWER 1: The Clarks used their sprinkler 15 hours.
T=40hrs-C=40hrs-15hrs=25 hrs The Thomases used their sprinkler 25 hours.
CHECK:
35L/hr(25 hrs)+15L/hr(15)=1100L
875L+225L=1100L
1100L=1100L