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Malcolm is making 12 pounds of fruit salad with pineapple and strawberries. Pineapples cost $7.50 per pound and strawberries cost $10.50 per pound. How many pounds of pineapple and how many pounds of strawberries should Malcolm use for the mixture to cost $9 per pound to make?

Sagot :

Answer:

6 pounds of strawberry

6 pounds of pineapples

Explanation:

Let,

s = number of pounds of strawberry

p = number of pounds of pineapples

Now we are told that Malcolm is making 12 pounds of fruit salad with pineapple and strawberries. This means

[tex]s+p=12[/tex]

Furthermore, we are also told that Pineapples cost $7.50 per pound and strawberries cost $10.50 per pound. This means that the cost of the mixture will be

[tex]7.50p+10.50s[/tex]

Therefore, the cost per pound of the mixture is

[tex]\frac{7.50p+10.50s}{12}[/tex]

which we are told is $9 per pound. Therefore,

[tex]\frac{7.50p+10.50s}{12}=9[/tex]

We can multiply both sides of the above equation by 12 and get:

[tex]7.50p+10.50s=9\times12[/tex][tex]7.50p+10.50s=108[/tex]

Hence, we have two equations and two unknowns:

[tex]\begin{gathered} p+s=12 \\ 7.50p+10.50s=108 \end{gathered}[/tex]

To solve the above system for s and p, we first solve for p in the first equation.

Subtracting s from both sides of the first equation gives

[tex]\begin{gathered} p+s=12 \\ \Rightarrow p=12-s \end{gathered}[/tex]

Substituting this value of p in the second equation gives

[tex]7.50(12-s)+10.50s=108[/tex]

which we expand to get

[tex]90-7.50s+10.50s=108[/tex][tex]90+3s=108[/tex]

Subtracting 90 from both sides gives

[tex]3s=108-90[/tex][tex]3s=18[/tex]

Finally, dividing both sides by 3 gives

[tex]s=18/3[/tex][tex]\boxed{s=6.}[/tex]

WIth the value of s in hand, we now find p.

[tex]p+s=12[/tex]

Putting s = 6 into the above equation gives

[tex]p+6=12[/tex]

subtracting 6 from both sides gives

[tex]\boxed{p=6.}[/tex]

Hence, s = 6 and p = 6. This means, 6 pounds of strawberry and 6