Step-by-step explanation:
466666666667/100000000000
I cannot see Zoe's work to explain the error, but the correct method of solving is listed:
x is the number of 30-second ads
y is the number of 60-second ads
x+y=12(60)=720 would be the first equation; this is because while the ads together make 12 minutes, the ad times are in seconds. This means we must multiply 12 by 60.
y=2x is the second equation
Our system is then
x+y=720
y=2x
We will use substitution to solve this. Plug 2x in place of y in the first equation:
x+2x = 720
Combine like terms:
3x = 720
Divide both sides by 3:
3x/3 = 720/3
x = 240
Substitute this value in for x in the second equation:
y=2(240)
y=480
Answer:
V = 23π/6
Step-by-step explanation:
V = 2π ∫ [a to b] (r * h) dx
y = −x² + 23x − 132
y = −(x² − 23x + 132)
y = −(x − 11) (x − 12)
Parabola intersects x-axis (line y = 0) at x = 11 and x = 12 ----> a = 11, b = 12
r = x
h = −x² + 23x − 132
V = 2π ∫ [11 to 12] x (−x² + 23x − 132) dx
V = 23π/6
