Question

A video rental company offers a plan that includes a membership fee of $7 and charges $1 for every DVD borrowed. They also offer a second plan, that costs $29 per month for unlimited DVD rentals. If a customer borrows enough DVDs in a month, the two plans cost the same amount. How many DVDs is that? What is that total cost of either plan? If a customer rents ___ DVDs, each option costs $___.

Answer 1

Answers:

If a customer rents 22 DVDs, each option costs $29

This only applies to one month.

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Work Shown:

x = number of DVDs borrowed

y = total cost

Plan A has a cost of x+7 dollars since x represents the cost of renting the x DVDs plus the membership fee of $7. We can say y = x+7.

Plan B has a fixed cost of $29 per month, so y = 29. There is no x here to worry about as the cost is the same no matter how many DVDs you rent.

y = x+7 and y = 29 are dealing with the same y value. We can use substitution to solve for x

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y = 29 ... start with second equation

x+7 = 29 .... replace y with x+7 (valid because y = x+7)

x+7-7 = 29-7 ... subtract 7 from both sides

x = 22

If the customer rents 22 DVDs, then plan A will charge y = x+7 = 22+7 = 29 dollars, which is the same as the flat rate cost plan B charges.

If the customer rents more than 22 DVDs per month, then its smarter to go with plan B (since plan A's cost will be larger). Otherwise, go for plan A.

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In terms of a graph, you can graph both y = x+7 and y = 29 together on the same xy axis. The line y = x+7 goes through (0,7) and (1,8). The line y = 29 goes through (0,29) and (1,29). Both lines intersect at (22,29) to indicate that x = 22 and y = 29 pair up together.