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A patient takes vitamin pills. Each day she must have at least 150 IU of vitamin \( \mathrm{A}, 3 \mathrm{mg} \) of vitamin \( \mathrm{B}_{1} \), and 60 mg of vitamin C . She can choose between pill 1 , which contains 90 IU of vitamin \( \mathrm{A}, 1 \mathrm{mg} \) of vitamin \( \mathrm{B}_{1} \), and 10 mg of vitamin C , and pill 2 , which contains 30 IU of vitamin \( \mathrm{A}, 1 \mathrm{mg} \) of vitamin \( \mathrm{B}_{1} \), and 40 mg of vitamin C . Pill 1 costs \( 10 \phi \), and pill 2 costs \( 20 \phi \). How many of each pill should she buy in order to minimize her cost? What is the minimum cost? She should buy \( \square \) of pill 1 and \( \square \) of pill 2 . The minimum cost is \( \$ \square \). (Simplify your answers. Type integers or decimals.)

Ask by Ward Williams. in the United States
Mar 09,2025

Upstudy AI Solution

Tutor-Verified Answer

Answer

She should buy 2 of pill 1 and 1 of pill 2. The minimum cost is \$40.

Solution

The decision variables are: - \( x \) = number of pill 1. - \( y \) = number of pill 2. Each pill contains: - Pill 1: \( 90 \) IU vitamin \( \mathrm{A} \), \( 1 \) mg vitamin \( \mathrm{B}_1 \), and \( 10 \) mg vitamin C. - Pill 2: \( 30 \) IU vitamin \( \mathrm{A} \), \( 1 \) mg vitamin \( \mathrm{B}_1 \), and \( 40 \) mg vitamin C. The cost function is: \[ \text{Minimize } C = 10x + 20y. \] The vitamin requirements impose the following constraints: 1. Vitamin \( \mathrm{A} \): \[ 90x + 30y \ge 150. \] Dividing by \( 30 \): \[ 3x + y \ge 5. \] 2. Vitamin \( \mathrm{B}_1 \): \[ x + y \ge 3. \] 3. Vitamin C: \[ 10x + 40y \ge 60. \] Dividing by \( 10 \): \[ x + 4y \ge 6. \] Also, we have: \[ x \ge 0,\quad y \ge 0. \] To find the minimum cost, we examine the intersections of the constraint boundaries. **Step 1. Intersection of \( 3x+y = 5 \) and \( x+y = 3 \):** Subtract the second from the first: \[ (3x+y) - (x+y) = 5 - 3 \quad \Longrightarrow \quad 2x = 2 \quad \Longrightarrow \quad x = 1. \] Substitute into \( x+y = 3 \): \[ 1 + y = 3 \quad \Longrightarrow \quad y = 2. \] Candidate: \( (1,2) \). **Step 2. Intersection of \( x+y = 3 \) and \( x+4y = 6 \):** Subtract the first from the second: \[ (x+4y) - (x+y) = 6 - 3 \quad \Longrightarrow \quad 3y = 3 \quad \Longrightarrow \quad y = 1. \] Then from \( x+y = 3 \): \[ x + 1 = 3 \quad \Longrightarrow \quad x = 2. \] Candidate: \( (2,1) \). **Step 3. Intersection of \( 3x+y = 5 \) and \( x+4y = 6 \):** Express \( y \) from the first equation: \[ y = 5 - 3x. \] Substitute into \( x+4y=6 \): \[ x + 4(5 - 3x) = 6 \quad \Longrightarrow \quad x + 20 - 12x = 6, \] \[ -11x = 6 - 20 \quad \Longrightarrow \quad -11x = -14 \quad \Longrightarrow \quad x = \frac{14}{11}. \] Then, \[ y = 5 - 3\left(\frac{14}{11}\right) = 5 - \frac{42}{11} = \frac{55 - 42}{11} = \frac{13}{11}. \] However, check the vitamin \( \mathrm{B}_1 \) constraint: \[ x+y = \frac{14}{11} + \frac{13}{11} = \frac{27}{11} \approx 2.45 < 3. \] So this candidate is not feasible. **Step 4. Evaluate the cost at the feasible candidates:** For \( (1,2) \): \[ C = 10(1) + 20(2) = 10 + 40 = 50. \] For \( (2,1) \): \[ C = 10(2) + 20(1) = 20 + 20 = 40. \] **Step 5. Verify feasibility of \( (2,1) \):** - Vitamin \( \mathrm{A} \): \[ 90(2) + 30(1) = 180 + 30 = 210 \ge 150. \] - Vitamin \( \mathrm{B}_1 \): \[ 2 + 1 = 3 \ge 3. \] - Vitamin C: \[ 10(2) + 40(1) = 20 + 40 = 60 \ge 60. \] All requirements are met. **Final Answer:** She should buy \( 2 \) of pill 1 and \( 1 \) of pill 2. The minimum cost is \( \$40 \).

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Mind Expander

To solve this problem, we need to set up a system of inequalities based on the vitamin requirements and analyze cost minimization. Let's define: - \( x \) = number of pill 1 - \( y \) = number of pill 2 We create the following inequalities based on the vitamin contents: 1. For vitamin \( A \): \[ 90x + 30y \geq 150 \] 2. For vitamin \( B_1 \): \[ x + y \geq 3 \] 3. For vitamin C: \[ 10x + 40y \geq 60 \] The cost function to minimize is: \[ Cost = 10x + 20y \] Now let's simplify and solve the inequalities: 1. From \( 90x + 30y \geq 150 \): \[ 3x + y \geq 5 \quad \text{(dividing the whole inequality by 30)} \] 2. The second inequality remains: \[ x + y \geq 3 \] 3. From \( 10x + 40y \geq 60 \): \[ x + 4y \geq 6 \quad \text{(dividing the whole inequality by 10)} \] Now let's graph these inequalities: - \( y \geq 5 - 3x \) (from the first) - \( y \geq 3 - x \) (from the second) - \( y \geq \frac{6 - x}{4} \) (from the third) To find the feasible region, we can plot these inequalities on a graph and find the intersection points. Next, we calculate the points: 1. \( x = 0 \): - From \( 3y \geq 5 \) → \( y \geq \frac{5}{3} \approx 1.67 \) - From \( y \geq 3 \) → \( y=3 \) - From \( y \geq \frac{6}{4} = 1.5 \) 2. \( x = 1 \): - \( y \geq 2 \) (from \( y \geq 3 - x \)) - \( y \geq 1.5 \) 3. \( x = 2 \): - \( y \geq 4 \) (no solutions) Finally, solving \( (3,0) \) and \( (0,3) \) and calculating costs find valid integers. After checking various combinations, we find: - \( x = 3 \) and \( y = 0 \) gives: Cost = \( 10(3) + 20(0) = 30 \) - \( x = 0 \) and \( y = 3 \) gives: Cost = \( 10(0) + 20(3) = 60 \) - The valid minimum is found at \( (2, 1) \): Cost = \( 10(2) + 20(1) = 60 \) Therefore, she should buy \( 2 \) of pill 1 and \( 1 \) of pill 2. The minimum cost is \( \$ 60 \).

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