Pip e +====+ What is the length of the shortest pipe, of inter | Programming Challenges - How to be a breathtaking Programmer

Pip e
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What is the length of the shortest pipe, of internal radius 50mm, that can fully contain 21 balls of radii 30mm, 31mm, ..., 50mm?

Give your answer in micrometres (10-6 m) rounded to the nearest integer.
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Thank you to Rishabh for suggesting this challenge!