The sum first 9 term of an arithmetic sequence is 90. What is its 5th term

Question

The sum first 9 term of an arithmetic sequence is 90. What is its 5th term

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Aubrey 1 month 2021-08-18T16:36:38+00:00 2 Answers 1 views 0

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    0
    2021-08-18T16:38:12+00:00

    Answer:

    it’s 50 because if it is 9 term than 90 then 5 means 50 and if this is wrong the sorry because I am studying in 7th STD only

    0
    2021-08-18T16:38:31+00:00

    Given ,

    The sum first 9 term of an arithmetic sequence is 90

    We know that , the sum of first n terms of an AP is given by

     \boxed{  \sf{S_{n} =  \frac{n}{2}  \{2a + (n - 1)d \}}}

    Thus ,

    \sf \mapsto 90 = \frac{9}{2}  \{ 2a + (9 - 1)d \} \\  \\  \sf \mapsto 90 =  \frac{9}{2} (2a + 8d) \\  \\\sf \mapsto  10 =  \frac{2}{2} (a + 4d) \\  \\\sf \mapsto  a + 4d = 10

    Now , the 5th term will be

    a + (5 – 1)d

    a + 4d

    10

    Therefore ,

    • The 5th term of AP is 10

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