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Activity Discussion Math Arithmetic fun Reply To: Arithmetic fun

  • Rajesh

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    June 25, 2023 at 5:02 pm
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    Given that AP is 27, 24, 21 …

    a1 = 30 ;a2=27; a3 = 24 and d =a2-a1= 27- 30 = (-3) ; sn =0 (given )

    We know that

    Sn=n/2 [2a+(n−1)d]

    Since the sum is 0,

    n/2[2×30+(n−1)(−3)]=0

    n(60−3n+3)=0

    n(60−3n)=0

    n=0 and 60−3n=0

    60=3n

    n = 60/3

    n = 20

    ∴n=0 and n=20

    Since the number of terms cannot be equal to 0 so number of terms (n) = 20

    • This reply was modified 11 months ago by  Rajesh Saini. Reason: Type mistake
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