Creating Linear Inequalities

Question

Lisa wants to buy some DVD’s online. Each DVD costs $11.99 and shipping for the whole order is $9.99. She has no more than $300 to spend. How many DVD’s can Lisa order without exceeding her $300 limit?

Answer 1

Hello, Giselle,

Patrick's answer is correct if the sipping for EACH DVD is $9.99. However, you state for the WHOLE order, so I suggest the following alternative4 analysis.

Money left after shipping any number of DVD's: $300 - 9.99 = 290.01

Divide that by the cost for each DVD: 290.01/11.99 = 24.19 DVD's

Lisa can buy up to 24 DVD's if they are all sent in the same shipment (the whole order). She'll also have $2.25 left to buy some gum.

Bob

Answer 2

Hi Giselle!

Good question! Let's start by looking at what we know. Since the total order is going to take $9.99 for shipping, let's take that out of the original $300 maximum left to spend. That's going to be the amount that we can use to calculate the number of DVD's that can be purchased.

$300 - $9.99 = remaining money

= $290.01

So this remaining amount is the maximum amount that can be spent on x DVDs (at $11.99 apiece), or, in mathematical sentences...

$290.01 < $11.99x, where x is a whole number (it sucks to have part of a DVD)

24.18 < x, so the whole number would be 24.

Just to be certain, let's check our work!

$11.99 * 24 + $9.99 = $297.75.

That makes sense, since she won't be able to use the remaining $2.25 to purchase any more DVD's!

Hope that helps -- let me know if you have any questions!

Niral

Answer 3

300/(11.99 + 9.99) =

300/(21.98)

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