Maths! How do you find the inner surface area of a piece of conduit in m squared?

Question

It has an outer diameter of 25mm, an inner diameter of 10mm and is 5m long.

Answer 1

inner surface area of a conduit of inner diameter d and length l = pi*d*h
herd d = 10mm= 0.01 m
and h = 5m
so inner surface area = pi*0.01*5
= 0.157 m squared

Answer 2

Giving you the outer diameter is a red herring.

The inside diameter is 10 mm

This 10/1000 m or 1/100 m or 0.01 m

The inside surface area = pi x inside diameter x length

= pi X 0.01 x 5 = 0.1570 m^2 = 0.157 m^2 (3sf)

Answer 3

pi times diameter = circumference.
So.
The inner cirumference of your conduit is 22/7 x 10mm.
= 3.1428571 x 10 = 31.428571 square mm.

Area = length x width.
Length = 5m (5000mm)
Width (when opened up) is the inner circumference = 31.428571.

Therefore the inner surface area = 31.428571 x 5000 = 157142.85 square mm.
Divide this by 1,000,000 to get square metres = 0.1571428

Answer 4

The inner diameter is converted to 0.10 meters first. Then find the radius 0.005 meters. To calculate the inner surface area, we multiply pi (3.1415926) by the radius squared (0.000025 m squared) by the length (5 meters). The value for pi can be rounded anywhere and give an approximation. I chose 7 places to get a more accurate value. The solution is about 0.000392699075 cubic meters.

Answer 5

Pi x 0.01 x 5 = m^2