Question

A. Jenna wants to buy a new tablet computer. Top Quality, an electronics store, is selling them at a 15% discount off the list price.

Using t as the list price of the tablet, write two different expressions representing the discounted price.

B. Explain how each expression represents the discounted price.

C. While at Top Quality, Jenna sees a smartphone on sale for 14 off its list price. Her friend tells her to wait and buy it at Big Value, a discount chain, where the same phone is selling for only 75% of the list price.

Should Jenna buy the smartphone at Top Quality or Big Value? Support your answer with mathematical evidence. (Assume that getting the lowest price is Jenna's only consideration.)

Answer 1

Explanation:

Part A

Cost = T - (15/100) * T

Cost = (85/100)*T

Part B

You are asked to take 15% off the cost of something. The first equation is very clear how to do that -- just take 15% of T away from T

The second part is not so obvious if you are not familiar with it, but the result will be the same.

Start with the first equation

Cost = T - (15/100) T Change 1 T to 100 / 100

Cost = 100*T/100T - 15/100T

Cost = 85 /100 * T

Part C

Cost = Phone - 14 at Top quality. Red in Graph below

Cost = 75/100 * Phone at Big value. Blue in Graph belos

The graph below is a good way to answer this. I won't solve it algebraically when the graph will give you a much better idea which phone to get.

Answer: Up to a phone cost of 55 dollars, the red phone is the better buy.

After 55$ the blue phone is better.

Try this with a couple of values for phone,