7) David bought a computer that was 20% off the regular price of $1080. If an 8% sales tax was added to the cost of the computer
, what was the total price David paid? 8) Suzanne bought a sweater at the sale price of $25. The original cost of the sweater was $40. What percent represents the discount that Suzanne received when buying the sweater?
9) Leo bought a used car for x dollars. One year later the value of the car was 0.88 x. Which expression is another way to describe the change in the value of the car?
7. Okay. So the computer was originally $1,080, and the discount is 20%, but David would still have to pay 80% of the original price. To find the sale price, let's multiply. 1,080 * 80% (0.8) is 864. The sale price of the compuet is $864, but now we must add the sales tax to find the total price. We will multiply by 108%, because 100% (representing the price + 8% is 108%, and doing this will get us stright to the total price. 864 * 108% (1.08) is 933.12. There. David paid a total price of $933.12 for the computer.
8. Okay. So we are looking for the amount of discount for the sweater Suzanne bought. First off, let's subtract the prices to find the difference. 40 - 25 is 15. Now, let's divide that by 40 (the original price) to find the discount. 15/40 is 0.375. Or 37.5% when converted into a percentage. There. Suzanne received a 37.5% discount on the sweater when she bought it.
9. So the car was bought for x dollars. 0.88 represents 88%, so the value of the car is 88% of the previous year. An expression that is a way to describe the change in car value is x * (100 - 0.12)^t, because you car loses 12% of the remaining value each year, which leaves 88% of it remaining, and having the t as the exponent represents the number of years. That expression helps find the value of the car currently and can help you compare the values.
-t + 9t - 12t - (-16t) - 18t = -6 -t + 9t - 12t + 16t - 18t = -6 -6t = -6 -6t/-6 = -6/-6 (-6 on the left side cancels out so we are only left with T and our answer) T = 1
