Question 1159726
L, the low price or low concentration
H, the high price or high concentration
T, the target price or concentration
v, the amount of the H material
M, the amount of the mixture of H and L


{{{Hv+L(M-v)=TM}}}
-
{{{Hv-Lv+ML=MT}}}
{{{(H-L)v=MT-ML}}}
{{{highlight(v=M((T-L)/(H-L)))}}}



Your example:
{{{v=30((3.56-3.3)/(3.95-3.3))}}}

{{{v=30(0.26/0.65)}}}

{{{highlight(v=12)}}}---------kilograms of the $3.95 per kilogram cookies.
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{{{highlight(18)}}}----------kg of the $3.3 per kg cookies.