PLEASE HELP!

G

Guest

Guest
Cashews sell for $12 per pound, and peanuts for $5 per pound, at a local candy store. The manager of the store wants to prepare 70 pounds of a mix that will sell for $10 per pound. Determine the amount of cashews and peanuts that should be used for the mix.

This is what I found, but it was incorrect:

x=cashews, y=peanuts x+y=70lb = $10/lb

12x+ 5y=10
12(5) + 5(2)= 10
60 + 10=70 lb

5 lb cashews, 2 lb peanuts
 
It would probably help if you clearly stated what you mean "x" and "y" to stand for, and perhaps also if you used units, so you could tell if you were setting the same sorts of things equal. Also, how did you get that x = 5 and y = 2? I don't see where you solved for those numbers; they just sort of "appear"...? And since 5 + 2 doesn't equal seventy, I'm not sure why you think this would be a valid solution...?

. . . . .pounds:
. . . . .cashews: c
. . . . .peanuts: p
. . . . .mix: c + p = 70

. . . . .unit cost:
. . . . .cashews: 12
. . . . .peanuts: 5
. . . . .mix: 10

Note: Since the "mix" cost is closer to the cost of the cashews, you should expect to be putting more cashews into the mix.

. . . . .total cost:
. . . . .cashews: 12(c)
. . . . .peanuts: 5(??)
. . . . .mix: ???

Complete the table. Add the input costs; set equal to the output cost. This equation, along with the first equation relating the weights, gives you two equations in two variables. Solve the system.

If you get stuck, please reply showing how far you have gotten. Thank you.

Eliz.
 
stapel, I came up with 5 and 2 because 5 lb of cashews times $12 equals 60, and 2lb peanuts times $5 equals $70. I don't understand what you are telling me.
 
She's telling you to solve the two equations
12x+ 5y=10(x+y) and
x+y=70
---------------
Gene
 
Is this right?

12x + 5y= 10(x+y)

12x + 5y= 10x + 10y

2x=5y

2(35)=5(14)

70=70

35 lb of cashews and 14 lb of peanuts
 
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