Question 675257
Two pipes are used to fill a water storage tank. The first pipe can fill the tank in 4 hours, and the two pipes together can fill the tank in 2 hours less time than the second pipe alone. How long would it take for the second pipe to fill the tank?
-------
1st pipe rate is 1/4 job/hr
-----
2nd pipe rate is 1/x job/hr
------
Together rate is 1/(x-2) job/hr
----------
Equation:
rate + rate = together rate
---
1/4 + 1/x = 1/(x-2)
---
x(x-2) + 4(x-2) = 4x
-----
x^2 - 2x + 4x-8 = 4x
------
x^2 -2x - 8 = 0
---
Factor:
(x-4)(x+2) = 0
---
Positive solution:
x = 4 hrs (time for the 2nd pipe to do the job)
---
x-2 = 2 hrs (time for the 2 pipes to do the job together)
============
Cheers,
Stan H.