Question 629163
   <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi,
dilute the 70% alcohol solution into 20% alcohol solution using{{{highlight(x)}}} <u>sterile H2O</u>
  water = water
 x + .30A = .80(A+x)
      .20x = .5A
         x = .5A/.2
         x = 2.5A     Add 2.5 times as much water as the amount of 70% solution used

For ex:  using 10L of 70% solution  &#8658;  {{{25 + .30*10 = .80*35 = 28}}}