Abstract
We prove that, for any covering of a unit d-dimensional Euclidean ball by smaller balls, the sum of radii of the balls from the covering is greater than d. We also investigate the problem of finding lower and upper bounds for the sum of powers of radii of the balls covering a unit ball.

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Acknowledgements
The author would like to thank Arseniy Akopyan and Alexandr Polyanskii for bringing this problem to his attention and for invaluable discussions. The author was supported in part by NSF Grant DMS-1400876.
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Glazyrin, A. Covering a Ball by Smaller Balls. Discrete Comput Geom 62, 781–787 (2019). https://doi.org/10.1007/s00454-018-0010-4
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DOI: https://doi.org/10.1007/s00454-018-0010-4