area of parallelogram

Question

A cylinder well has 14 cm thick wall and its depth is 20 m. If the diameter of the outer circle of the wall is 3.08m. Find the area of its inner curved surface.

Answer 1

Let...

d_o= outer diameter = 3.08m = 308cm

d_i = inner diameter = d_o-2(d_i)

                             = 308-2(14)

                             = 308-28

                             = 280cm

                             = 2.80m

 

We know that...

    C_i=πd_i............circumference equals "pi" times diameter.

      =3.14(280)...substitute values

      =879.65cm...simplify

∴ C_i=8.80m........this is the horizontal dimension of the rectangle 

                          when the inner surface is "unfolded" flat in two 

                          dimensions.

 

The depth of the well is 20m which is the vertical dimension of 

                          the rectangle, prob statement, given.

 

So the area of the inner curved surface (A) is...

   A = 20(8.8) = 175.93m²

 

Watch your units!

Answer 2

Hi Sam, the surface area of the inner circle is given by: S(urface area) = pi * d(iameter) * h(eight). We are given the diameter of the outer circle, 3.08 m, and the thickness of the well wall, 14 cm.

 

To find the diameter of the inner circle, we need to subtract 2 times the thickness of the well wall from the diameter of the outer circle. Remember, the well wall thickness occurs on both ends of the outer circle's diameter.

 

Diameter of inner circle = 3.08 - .28 = 2.80 meters.

 

Surface area based on the diameter of the inner circle:

 

S = pi * d * h

 

pi = 3.14

d = 2.80 meters

h = 20 meters

 

S = 3.14 * 2.80 m * 20 m

 

S ≈ 175.84 m²

 

Questions?