18.
Use the formula for the circumference of a circle.
[tex] C = 2 \pi r[/tex]
Now enter the information you are given. You are told the circumference is 28pi, so replace C with 28pi and solve for r, the radius.
[tex] 28 \pi = 2 \pi r[/tex]
Switch the sides.
[tex] 2 \pi r = 28 \pi [/tex]
Divide both sides by 2pi.
[tex] \dfrac{2 \pi r}{2 \pi} = \dfrac{28 \pi}{2 \pi} [/tex]
[tex] r = 14 [/tex]
Answer: B 14 m
19.
Look at a point on the graph. For example, when x = 4, y = 2 which is point (4, 2). x represents the number of songs. y represents the cost. The point (4, 2) means that 4 songs cost $2. Divide $2 per 4 to find a unit rate of cost of songs. $2/4 = $0.5 per song. Each song costs $0.50. If you multiply the number of songs by 0.5, you get the cost in dollars. The number of songs is x. The price of x songs is 0.50x. The price is y, so the equation is y = 0.50x.
Answer: B y = 0.50x
