1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Word Problem - Please Help -

  1. Jun 26, 2005 #1
    1. A tank holds 90 L of chemical solution. Currently the solution has a strength of 20%. How much of this should be drained and replaced with an 80% solution to have a final strength of 30%?
  2. jcsd
  3. Jun 26, 2005 #2


    User Avatar
    Science Advisor

    Suppose you "drain and replace" X liters of the 20% solution. That leaves 90- X liters of 20% solution. The X liters of the 80% solution will contain 0.8X L of the chemical. The remaining 90-X liters will contain 0.2(90- X) L of the chemical so you will now have 0.8X+ 0.2(90-X) L of the chemical in the final result. How much chemical will there be in 90 L of 30% solution? Set those equal and solve for X.
  4. Jun 26, 2005 #3
    Answer is 15 L.

    thx :D
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook