hmm, interesting Q
a ball is a sphere, therefore it could hv a ball in the middle and that ball is surrounded by other balls .... the middle layer would hv maximum balls, say n number of balls and then the next layers on its two sides would be n-1, something like the equation below:
...., n-2, n-1, n, n-1, n-2, ....
so when you take, n = 10 ... the equation gets solved
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