Here's the question you clicked on:
stupidinmath
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u can use first of all use the folllowing formula for finding out the volume of the triangular pipe... i.e.. (area of triangle) (height) and in this case the height is 10m... and now.. find the volume of one pipe using the formula pi r^2h and then multiply it with 3.... and then subtract the result from the volume of triangular pipe... make sure... that the side of of triangle has been given in cm and the length in m.... and... for finding the radius... just think over the question a little... :D... and if still any problem comes feel free to ask.. i would be really very happy in answering and solving ur doubt... because this question is a bit twisted...