The Hill family and the Stewart family each used their sprinklers last summer. The water output rate for the Hill family's sprinkler was 15 L per hour. The
water output rate for the Stewart family's sprinkler was 25 L per hour. The families used their sprinklers for a combined total of 55 hours, resulting in a
total water output of 1025 L. How long was each sprinkler used?
Let
x ------> the number of hours of Hill family's sprinkler
y ------> the number of hours of Stewart family sprinkler
so
we have that
x+y=55 -------> x=55-y ------> equation 1
15x+25y=1025 ------> equation 2
Solve the system
Substitute equation 1 in equation 2
15(55-y)+25y=1025
solve for y
825-15y+25y=1025
10y=1025-825
10y=200
y=20
Find the value of x
x=55-20) -----> x=35
therefore
Hill family's sprinkler: 35 hours
Stewart family's sprinkler:20 hours