Question

the surface area of a cylinder is 289cm^2 the height is 21cm what is the diameter

Answer 1

do u know the relationship between radius and surface area?

Answer 2

no

Answer 3

surface area is the area of the outside: so for a cylinder imagine us split it up the length and unfold it
you'll be left with 2 circles and a rectangle

Answer 4

surface area equals sums of area of each shape
so area of a circle equation =
and area of a rectangle eqn =

Answer 5

reply on a drawing, top right when mouse over pic

Answer 6

circumference of a circle = 2 pi r
... u with me still trevor?

Answer 7

yes

Answer 8

cool, then:
so area of a circle equation = ???
and area of a rectangle eqn = ???
@trevor215

Answer 9

7.5=area of the circle

Answer 10

no sorry i got mixed up with another problem thats not the area

Answer 11

so what are your equations to work out the area of a circle?

Answer 12

and area of a rectangle?

Answer 13

k... ill get u started:
Equation for area of a rectangle is:
Area = Length x Width

now u go: circle

Answer 14

Equation for area of a rectangle is:
Area = Length x Width
in this case, the Length = height of cylinder = 21
and the width = the same as the circumference of one of the circles = 2*pi*r
so area of the rectangle = 21 * 2 * pi * r

now what are the area's of the circles @trevor215 ?

Answer 15

idk how to get the radius

Answer 16

ignore the radius for now, just leave it as r
so what's the equation for area of a circle

Answer 17

4 pi r 2