Answer:
a: 
Step-by-step explanation:
Answer:
a
Step-by-step explanation:
Answer:
Step-by-step explanation:
For 
, we have two cases:
Therefore, for 
, we have the following cases:
Solving, we have:
.
Therefore,
the radius: r^2 = 81
r =9
c = 2*pi*r
= 2 * pi * 9
= 18 *pi
Answer: 18*pi or approximately 56.62
Answer: 98.1%
Explanation:
A 10% sale means that the post-sale price of the item is now 90%, or 0.9 of the original cost of the item. We then apply 9% sales tax by multiplying the 0.9 by 109%, or 1.09. 0.9 * 1.09 = .981, so the total cost of the item is 98.1% of the original pre-sale sticker price.
For percentage problems that do not deal with a specific starting number, it is always helpful to plug in 100 for the starting number. Here, we would then have a post-sale price of 90 dollars, and if we calculate the sales tax for the 90-dollar item it would be 90 * 0.09 = $8.10. THis gives us a total cost of 90 + 8.10 = $98.10, or 98.1% of the original 100-dollar price.
