Question

find the total surface of a hollow cylinder open at both ends if the length is 12 CM external diameter 10 cm and thickness 2 cm

Answer 1

Answer:

Step-by-step explanation:

What is a better way to understand a problem than visualise it. So, let us draw a figure of the cylinder as below:-

As we can see there are four separate geometrical areas that make the hollow cylinder. Two curved areas in cylindrical form and two identical flat areas on the top and bottom between two concentric circles.

Area of the outer cylinder =2πRh, (R=7 cm, h=22 cm)

→2π*7*22 =308π cm²

Area of the inner cylinder =2πrh, (r=6 cm)

→2π6*22 =264π cm²

Top and bottom areas =2*{π*7²-π*6²} =2*13π =26π cm²

So total area = 308π+264π+26π =598π cm² ≈1878.67 cm²

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Answer 2

the formula to find it's answer is
$2\pi \times radius1 \times hight + 2\pi \times radius2\times hight$
ie 2πh(radius1+radius2)
ie 2×3.14×12(5+3)
=602.88cm2