Sum of first 55 terms in an A.P. is 3300, find its 20th term.​

Sum of first 55 terms in an A.P. is 3300, find its 20th term.​

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2 thoughts on “Sum of first 55 terms in an A.P. is 3300, find its 20th term.​”

  1. Correct Question:

    • Sum of first 55 terms of an AP is 3300, find it’s 28th term.

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    Given:

    • Sum of first 55 terms, (S₅₅) of AP is 3300

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    To find:

    • 20th term of AP (a₂₀)

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    Solution:

    • We have formula for sum of nth terms of AP::

    » Sₙ = n/2 [ { 2a + ( n-1 } d ]

    :: Substitute the value of n=55

    » S₅₅ = 55/2 [ { 2a + ( 55-1 ) d } ]

    :: Put value of S₅₅=3300

    » 3300 = 55/2 [ { 2a + 54d } ]

    :: Now transport 55/2 from RHS to LHS

    [ It will change into its recipocated form after transportation]

    » 3300 × 2/55 = 2a + 54d

    :: Now divide both sides by 2

    » [ 3300 × (2/55) ] ÷ 2 = ( 2a + 54d ) ÷ 2

    :: Now solving it

    » 3300/55 = a + 27d

    » 60 = a + 27d

    » 60 = a₂₈

    Hence the required 28th term of AP is 60.

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  2. Answer:

    [tex]it \: is \: given \: that \\ n = 55 \\ ap = 3300 \\ \\ we \: know \: that \\ {s}^{55} = \frac{55}{2} (2a + 55 – 1)d \\ 3300 = \frac{55}{2} (2a + 54d) \\ 3300 = 55(a + 27d) \\ \frac{3300}{55} = a + 27d \\ a + 27d = 60..1equation \\ now \: n = 28 \\ \\ t = a + (n – 1)d \\ t = a +( 28 – 1)d \\ t = a + 27d \\ t = 60 \\ \\ twenty \: eight \: term \: of \: ap \: is \: 60 \\ hence \: 28 \: term \: is \: 60[/tex]

    I hope it’s helpful for you

    so much time gone for your question

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