Hi,

I have an engineering question in a struggling to solve.

I have a Second Moment of Area question, where I need to replace a solid cylindrical beam with a hollow one.

For the solid beam, the second moment of area is:

For the hollow beam, the external diameter (D) needs to be x2.5 the internal diameter (d), therefore d=D/2.5

The formula I need to rearrange to make "D" the subject is:

Any help is much appreciated

Kind regards

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