Question

Difficulty: EasySystems of Linear Inequalities in Two Variables

An artist sells small prints for 44 dollars each and large prints for 99 dollars each. The artist wants to sell at least 1515 prints in total and earn at least 8080 dollars from these sales. If the artist sells 55 small prints, what is the minimum number of large prints the artist must sell to meet both conditions?

Answer: 10 prints

Answer

The minimum number of large prints the artist must sell is 10.
Substituting the value of small prints (x=5x = 5) into the total count inequality x+y15x + y \geq 15 gives 5+y155 + y \geq 15, which simplifies to y10y \geq 10. Substituting it into the earnings inequality 4x+9y804x + 9y \geq 80 yields 20+9y8020 + 9y \geq 80, which simplifies to y6.67y \geq 6.67. To satisfy both conditions, the value of yy must be at least 10.

Step-by-Step Solution

1
Set up the inequalities for the system.
Let xx represent the number of small prints and yy represent the number of large prints. The constraint for the minimum number of prints is x+y15x + y \geq 15. The constraint for the minimum earnings is 4x+9y804x + 9y \geq 80.
To represent the given conditions as a system of linear inequalities in two variables.
2
Substitute the known value of small prints (x=5x = 5) into the inequalities.
Substituting x=5x = 5 into the first inequality gives 5+y155 + y \geq 15, which simplifies to y10y \geq 10. Substituting x=5x = 5 into the second inequality gives 4(5)+9y804(5) + 9y \geq 80, which simplifies to 20+9y8020 + 9y \geq 80, then 9y609y \geq 60, resulting in y2036.67y \geq \frac{20}{3} \approx 6.67.
To determine the range of values for the number of large prints (yy) under both constraints.
3
Determine the minimum integer value for yy that satisfies both inequalities.
The first constraint requires y10y \geq 10, and the second constraint requires y6.67y \geq 6.67. Since the number of prints must be an integer and both conditions must be satisfied, the minimum value is 1010.
To satisfy both inequalities simultaneously with the smallest possible integer value.

Key Concept

Systems of Linear Inequalities in Two Variables
Estimated Time:1m 0s
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