Question 1158001
If you start with v for how much of 75%, and 60-v for how much 50%, you can form equation   {{{75v+50(60-v)=65*60}}}, from which you will find:


{{{highlight(v=60((65-50)/(75-50)))}}}


You can see in this solution formula a possible easy way to form a necessary fraction, to multiply by the mixture size of 60L.




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More generally for two-part mixture,


H, the high concentration percent
L, the low conc percent
T, target conc. percent
M, the size of result mixture
v, amount of the H material


{{{Hv+L(M-v)=TM}}}

and solving this for v will give

{{{highlight(v=M((T-L)/(H-L)))}}}