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In an arithemetic sequence 20th term is 40 and common difference 5 find 5th and first term

By Clara

In an arithemetic sequence 20th term is 40 and common difference 5 find 5th and first term

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Clara

A team of eleven is to be chosen out of 16 cricket players of whom 4 are bowlers and 2
wicket keepers. In how many ways can t

in tbe given figure the diagonals of parallelogram ABCD intersect at O If Angle AOB=70 degree and angleDAC=30 degree find angle BD

1 thought on “In an arithemetic sequence 20th term is 40 and common difference 5 find 5th and first term”

  1. Answer:

    (a) x

    5

    =40,x

    10

    =20

    x

    10

    −x

    5

    =5d

    5d=20−40=−20

    ⇒d=−4

    Now, x

    15

    =x

    10

    +5d=20−20=0

    (b) First term, f=x

    5

    −4d=40−4(−4)=56

    S

    n

    =

    2

    n[2f+(n−1)d]

    ⇒0=

    2

    n[2×56+(n−1)(−4)]

    ⇒n(112−4n+4)=0

    ⇒n(116−4n)=0

    ⇒=0,n=29

    Thus, 29 terms of this sequence make the sum zero.

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