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Cherries cost $4/lb. Grapes cost $2.50/lb. You can spend no more than $15 on fruit,
and you need at least 4lb in all. Create a graph showing the amount of each fruit you can buy.
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The "solution " presented in the post by @josgarithmetic is incorrect
starting from the third line of his post to the end.
I came to bring you a correct solution.
x pounds of cherries
y pounds of grapes
Restrictions
4x + 2.5y <= 15,
x + y >= 4
x >= 0, y >= 0.
Plot the lines
y = -(4/2.5)x + 15/2.5 (red line in the plot below)
y = 4 - x (green line in the plot below)
The solution domain is in the first quadrant below the red line (including the red line)
and above the green line (including the green line).
So, the solutions are the points inside the triangle under the red line, attached to y-axis and above the blue line.
For example, x = 2, y = 2 is the solution (2 pounds of cherries and 2 pounds of grapes).
Solved in a right way, with complete explanations.
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Ignore the post by @jodgarithmetic, for the sake of safety of your mind.