• Q. First term is of arithmatic progression sequence is 42 and the difference between consecutive numbers is 7 , Find the sum numbers 15th, 16th, 17th, 18th and 19th terms.
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  • Sum of 15 position is (15/2)[2*42 + (15 - 1)x 7 ]

    = (7.5)[84 + (14)x 7 ]

    = (7.5)[84 + 98 ]

    = (7.5)[182]

    ie. S15 = (1365)

  • Sum of 16 position is (16/2)[2*42 + (16 - 1)x 7 ]

    = (8)[84 + (15)x 7 ]

    = (8)[84 + 105 ]

    = (8)[189]

    ie. S16 = (1512)

  • Sum of 17 position is (17/2)[2*42 + (17 - 1)x 7 ]

    = (8.5)[84 + (16)x 7 ]

    = (8.5)[84 + 112 ]

    = (8.5)[196]

    ie. S17 = (1666)

  • Sum of 18 position is (18/2)[2*42 + (18 - 1)x 7 ]

    = (9)[84 + (17)x 7 ]

    = (9)[84 + 119 ]

    = (9)[203]

    ie. S18 = (1827)

  • Sum of 19 position is (19/2)[2*42 + (19 - 1)x 7 ]

    = (9.5)[84 + (18)x 7 ]

    = (9.5)[84 + 126 ]

    = (9.5)[210]

    ie. S19 = (1995)

  • so the sequance of the sum numbers from position are.
    S15 = 1365
    S16 = 1512
    S17 = 1666
    S18 = 1827
    S19 = 1995

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