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A pet store owner wants to mix together an high quality dry cat food costing 1.10 per pound with a lower quality dry cat food costing 0.85 per pound. How many pounds of each should be mixed together in order to produce 40 pounds of a mixture costing 0.95 per pound?

I think I know how to start part of the problem but I am stuck on the second part of the problem. This is what I have gotten so far:

$$1.10x+0.85y= $$

Is this the right approach to this problem?

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Try working with the two equations, in two unknowns:

You can finish your first equation (sum of cost of more expensive food (x pounds at a cost of $1.10$) and the cost of the leass expensive food (y pounds at a cost of .85 per pound) by noting we want a total of $40$ pounds costing 0.95 per pound for a total cost of $.95\times 40$:

$$1.10x+0.85y= 0.95\times 40\tag{1}$$

The number of total pounds needed is the sum of the weights, in pounds, given by $x + y$: $$x + y = 40\tag{2}$$

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  • $\begingroup$ Let me know if you need some pointers for solving the "system" of two equations with two variables! $\endgroup$ – Namaste Apr 20 '13 at 3:59
  • $\begingroup$ Ugh, OP left everyone hanging! +1 $\endgroup$ – Amzoti Apr 21 '13 at 0:20
  • $\begingroup$ Yes...I've had a lot of that lately ;-) Hopefully, they've received the help they need...and just forget to "check back" or reply... $\endgroup$ – Namaste Apr 21 '13 at 0:23
  • $\begingroup$ You're welcome, Steven! $\endgroup$ – Namaste May 24 '13 at 4:45
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You are on the right track. Let x be the amount of expensive food and y the amount of cheap food. The equation you've already written is for the total cost, which we can extend to 1.10x+0.85y=40*0.95

You have two variables, so you need a second equation. The second equation I would use is x+y=40

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