data/problems/222.yml
---
:id: 222
:name: Sphere Packing
:url: https://projecteuler.net/problem=222
:content: |+
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<sup>-6</sup> m) rounded to the nearest integer.