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in Arithmetic Progression by (48.8k points)
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Find the value of the middle most term (s) of the AP : –11, –7, –3,..., 49.

1 Answer

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Best answer

Here, a = –11, d = –7 – (–11) = 4, an = 49 

We have an = a + (n – 1) d 

So, 49 = –11 + (n – 1) × 4 

i.e., 60 = (n – 1) × 4 

i.e., n = 16 

As n is an even number, there will be two middle terms which are 16/2th and (16/2 + 1)th, i.e., the 8th term and the 9th term.

a8 = a + 7d = –11 + 7 × 4 = 17 

a9 = a + 8d = –11 + 8 × 4 = 21 

So, the values of the two middle most terms are 17 and 21, respectively.

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