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Find the model of the total cost of Company A’s plan, using m for the minutes.

20 + 0.05 m

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Find the model of the total cost of Company B’s plan, using m for the minutes.

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Find out how many minutes of calling would make the two plans equal.

300 min

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If the person makes a monthly average of 200 min of calls, which plan should for the person choose?

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For the following exercises, use this scenario: A wireless carrier offers the following plans that a person is considering. The Family Plan: $90 monthly fee, unlimited talk and text on up to 5 lines, and data charges of $40 for each device for up to 2 GB of data per device. The Mobile Share Plan: $120 monthly fee for up to 10 devices, unlimited talk and text for all the lines, and data charges of $35 for each device up to a shared total of 10 GB of data. Use P for the number of devices that need data plans as part of their cost.

Find the model of the total cost of the Family Plan.

90 + 40 P

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Find the model of the total cost of the Mobile Share Plan.

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Assuming they stay under their data limit, find the number of devices that would make the two plans equal in cost.

6 devices

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If a family has 3 smart phones, which plan should they choose?

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For exercises 17 and 18, use this scenario: A retired woman has $50,000 to invest but needs to make $6,000 a year from the interest to meet certain living expenses. One bond investment pays 15% annual interest. The rest of it she wants to put in a CD that pays 7%.

If we let x be the amount the woman invests in the 15% bond, how much will she be able to invest in the CD?

50 , 000 x

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Set up and solve the equation for how much the woman should invest in each option to sustain a $6,000 annual return.

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Two planes fly in opposite directions. One travels 450 mi/h and the other 550 mi/h. How long will it take before they are 4,000 mi apart?

4 h

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Ben starts walking along a path at 4 mi/h. One and a half hours after Ben leaves, his sister Amanda begins jogging along the same path at 6 mi/h. How long will it be before Amanda catches up to Ben?

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Fiora starts riding her bike at 20 mi/h. After a while, she slows down to 12 mi/h, and maintains that speed for the rest of the trip. The whole trip of 70 mi takes her 4.5 h. For what distance did she travel at 20 mi/h?

She traveled for 2 h at 20 mi/h, or 40 miles.

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A chemistry teacher needs to mix a 30% salt solution with a 70% salt solution to make 20 qt of a 40% salt solution. How many quarts of each solution should the teacher mix to get the desired result?

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Paul has $20,000 to invest. His intent is to earn 11% interest on his investment. He can invest part of his money at 8% interest and part at 12% interest. How much does Paul need to invest in each option to make get a total 11% return on his $20,000?

$5,000 at 8% and $15,000 at 12%

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For the following exercises, use this scenario: A truck rental agency offers two kinds of plans. Plan A charges $75/wk plus $.10/mi driven. Plan B charges $100/wk plus $.05/mi driven.

Write the model equation for the cost of renting a truck with plan A.

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Practice Key Terms 3

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Source:  OpenStax, Algebra and trigonometry. OpenStax CNX. Nov 14, 2016 Download for free at https://legacy.cnx.org/content/col11758/1.6
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