Problem 222

Sphere Packing

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.

**
These problems are part of
Project Euler
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CC BY-NC-SA 2.0 UK
**