What quantity of 60 per cent acid solution must be mixed with a 20 solution to produce 640 mL of a 50 per cent solution?

Question

 x=60 per cent

y=20 per cent

x+y=640 mL at 50 per cent

Answer 1

Let x equal the amount of 60% solution.  Since you have a total of 640mL, then the amount of 20% solution is 640-x.

 

Using a table:  %           amount

                      .60              x          = .6x

                      .20       (640 - x)      = .2(640 - x) =   128 - .2x

                      .50            640        =  320

 

The amount must be equal giving you the equation:   .6x + (128 - .2x ) = 320

Combining like terms gives you:                                          .4x + 128 = 320    

 Subtracting 128 from both sides gives you:                                    .4x = 192

 Dividing both sides by .4 gives you:                                                  x = 480

 

Checking in your problem:  .6*480 + (128 - .2*480) = 288 + (128 - 96) = 288 + 32 = 320

 

 

You need 480 mL of 60% solution