Question 974226
Word problem into a rational equation, 18 lbs of fruit purchased, there where $9
worth of apples and $2.40 of bananas, price per lb of apples is three times more
than price per lb of bananas. How many lbs of apples and how many lbs of bananas
where purchased? How do I solve? 

My email is cyclo29@yahoo.com  thank you!
<pre>
Let the number of pounds of apples = x.
</pre>
>>18 lbs of fruit purchased<<
<pre>
So the number of pounds of bananas = 18-x
</pre>
price per lb of apples is three times more than price per lb of bananas.
<pre>
Let the price per pound of bananas = y
Then the price per pound of apples = 3y.
</pre>
>>...there where $9 worth of apples...<<
<pre>
{{{(matrix(6,1,
The,number,of,pounds,of,apples))}}}{{{"×"}}}{{{(matrix(6,1,
The,price,per,pound,of,apples))}}}{{{""=""}}}{{{"$9"}}}

Therefore:

(x)(3y) = 9
    3xy = 9
     xy = 3
</pre>
>>...and $2.40 of bananas,...<<
<pre>
{{{(matrix(6,1,
The,number,of,pounds,of,bananas))}}}{{{"×"}}}{{{(matrix(6,1,
The,price,per,pound,of,bananas))}}}{{{""=""}}}{{{"$2.40"}}}

Therefore:

(18-x)(y) = 2.40
  y(18-x) = 2.40
   18y-xy = 2.40

So we have the two equations:

{{{system(xy = 3,18y-xy=2.40)}}}

Substitute 3 for xy in the second equation:

 18y-xy = 2.40
  18y-3 = 2.40
    18y = 5.40
      y = 0.30, 

[so bananas sold for 30 cents a pound, and apples 90 cents a pound.]

Substitute y = 0.30 in the first equation:

     xy = 3
x(0.30) = 3
      x = {{{3/0.30}}}
      x = 10

So there were 10 pounds of apples purchased.
And therefore there were 18-x or 18-10 or 8 pounds of bananas.

Edwin</pre>