## butterflydreamer one year ago Question/picture attached below: http://prntscr.com/7ztnhm

1. butterflydreamer

Since each side of the xylophone has "n" wooden bars and there is an extra one in the centre, do we treat this as two series?

2. anonymous

well, there are $$2n+1$$ bars, so the $$2n$$ are from the left,right side, and then the $$1$$ is the middle. so you can just model it as the middle plus double a series for both sides

3. butterflydreamer

hmm.. so what if i did something like this? $S = \frac{ n }{ 2 } (20 + n(n-1)b) + \frac{ n+1 }{ 2 }(20 + nb)$

4. butterflydreamer

Just tested it by expanding and i eventually proved S = bn^2 + 20n + 10 so i guess it works :)

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