A hollow metal pipe of internal diameter 7cm and external diameter 8cm is 6.16m long calculate the volume of metal making the pipe in cubic centimetres​

The volume of the hollow metal pipe is approximately 72.571 cubic centimeters.

Step-by-step explanation:

The volume of the metal is the space occupied by the hollow pipe. Since it is a hollow cylinder, the volume (), in cubic centimetres, is defined by following expression:

(1)

Where:

- External and internal diameters, in centimetres.

- Length, in centimetres.

If we know that , and , then the volume of the hollow metal pipe is:

The volume of the hollow metal pipe is approximately 72.571 cubic centimeters.

The total volume of sand = pi/3*(6^2)*(15) + pi*(6)^2*(30) = 1260*pi mm^3 
So it will therefore take 1260*pi/10*pi = 126 seconds for all of the sand from the top hourglass to drip down to the bottom hourglass.