A 5-lb nut mixture is worth $2.80 per pound. The mixture contains peanuts worth $1.70 per pound and cashews worth $4.55 per pound. How many pounds of each type of nut are int he mixture?

2 Answers
Jun 4, 2015

Let's call the amount of cashew nuts x

Then the amount of peanuts is 5-x because we have 5 lbs in total.
5 lbs of mixture is 2.80*5=$14.00

This is equal to $1.70*(5-x)+$4.55*x=$14.00

Now work away the brackets first, keep all the x's on the left, and put the dollars to the right, divide, and you'll find x, the amount of cashew nuts. The rest is peanuts :-)

Jun 4, 2015

Let x in [0, 1] be the weight of cashews in one pound of mixture.

Then one pound of mixture contains (1-x) pounds of peanuts.

Equating the costs in dollars, we have:

2.80 = 1.70(1-x) + 4.55x

=1.70-1.70x+4.55x

=1.70+2.85x

Subtract 1.70 from both ends to get:

2.85x = 1.10

So x = 1.10/2.85 = 110/285 = 22/57 pounds of cashews per pound of mixture

and 1-x = 1-22/57 = 35/57 pounds of peanuts per pound of mixture

In 5-lb of mixture there is 5*22/57 ~= 1.93 lb of cashews
and 5*35/57 ~= 3.07 lb of peanuts.