Question 826814: Donna wants to make trail mix made up of almonds,walnuts and raisins.she wants to mix one part almonds,two parts walnuts,and three parts raisins.almonds cost $12per pound,walnuts cost $9 per pound,and raisins cost $5 per pound.
Donna has $15 to spend on the trail mix.determine how many pounds of trail mix she can make.
Answer by josgarithmetic(39617)   (Show Source):
You can put this solution on YOUR website! a, w, r, the quantities of almonds, walnuts, and raisins.
The ratio wanted in a:w:r, is 1:2:3.
This ratio is based on six parts for the whole mix.
Accounting for money,
 = cost for almonds;
 = cost for walnuts
 = cost for raisins
The equation for cost according to the $15 restriction is 
Use the ratios to obtain two more equations.
Looking at the parts of the ratio, you see  , corresponding to  ; What next?
The mix contains 2 parts walnuts and 1 part almonds. Meaning is  ; Anything else?
Almonds 1 part, raisins 3 parts. Meaning is  .
That all might be enough to work with.
Can the money equation be expressed in just ONE variable?
Look at the equations from the ratio:
 ;  ;  .
Obvious substitutions now ready for w and r.
Restate money equation:
'
Make the substitutions:
 , expressed only in the single variable, a for the almonds.
'
Solving ...
 -----(not yet full pound, so wondering if made a mistake somewhere).
'
, 
'
, 
'
The results should really be checked to see if these quantities really do give a cost of $15.
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