A cylinder with height 15 has a total surface area that is twice the area of a circle whose radius is 6 more than the radius of the cylinder. What is the radius of the cylinder?
I just need the equation, and I will solve it on my own.
2007-09-13 12:14:43 · 3 answers · asked by that's funny 3 in Science & Mathematics ➔ Mathematics
x = radius of cylinder
x+6 = radius of circle
Surface area of cylinder = 2pix^2 +2pixh
Area of circle = pi(x+6)^2
So 2pix^2 +2pixh = 2pi(x+6)^2
So with h=15, solve away.
2007-09-13 12:23:42 · answer #1 · answered by ironduke8159 7 · 0⤊ 0⤋
area of the cylinder=2pi rh=30pir
area of a circle with radius=r+6, is:pi(r+6)^2
now 30pir=2pi(r+6)^2
15r=(r+6)^2=r^2+12r+36
r^2-3r+36=0
2007-09-13 19:31:23 · answer #2 · answered by Anonymous · 0⤊ 0⤋
S = 2pi rh + 2 pi r^2 (surface area of sides and ends
S = 30pi r + 2pi r^2 = 2(pi (r+6)^2)
2007-09-13 19:22:47 · answer #3 · answered by holdm 7 · 0⤊ 0⤋