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If m is the average (arithmetic mean) of the first 10

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Re: If m is the average (arithmetic mean) of the first 10  [#permalink]

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New post 24 Feb 2018, 04:29
1
dave13 wrote:

what is difference between this formula For an arithmetic prog, Average = (first term + last term)/2 and this one \(x_n = a + d(n−1)\) ?

happy weekend :)


The two formulas are to find 2 different things.

Average = (first term + last term)/2 gives you the average of the AP. It could be the middle term if you have odd number of terms in the AP or it will be the average of two middle terms if you have even number of terms in the AP

\(x_n = a + d(n−1)\) gives us the nth term.

e.g.
AP = 3, 6, 9, 12, 15
a = first term = 3
d = common diff = 3
n = number of terms = 5

Average = (15 + 3)/2 = 9 (the middle term)

Second term = 3 + 3*(2 - 1) = 6
Third term = 3 + 3*(3 - 1) = 9
Fourth term = 3 + 3*(4 - 1) = 12
and so on...
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Re: If m is the average (arithmetic mean) of the first 10  [#permalink]

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New post 14 Mar 2019, 11:30
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Re: If m is the average (arithmetic mean) of the first 10   [#permalink] 14 Mar 2019, 11:30

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