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  Discussion about math, puzzles, games and fun.   Useful symbols: √ ∞ ≠ ≤ ≥ ≈ ⇒ ∈ Δ θ ∴ ∑ ∫ π -

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#1 2013-10-21 07:19:10

ninjaman
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geometric series

hello

I have the first term of 30 and the last of 300, I have 7 speeds, 30 is first and 300 is last
I have to find the ratio, to find the middle speed.
im lost, should I be rearranging the formula?smile

#2 2013-10-21 08:42:45

Nehushtan
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Re: geometric series

To find the middle term of a G.P. with positive terms, you dont need to find the common ratio: just multiply the two end terms and take the square root (i.e. take the geometric mean).

Similarly to find the middle term of an A.P., you dont need the common difference: just add the two end terms and divide by 2 (arithmetic mean).

Last edited by Nehushtan (2013-10-21 22:36:14)


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