Sequences and Series


  1. The next number of the sequence 2, 6, 12, 20, 30, 42, 56, ___ is









  1. View Hint View Answer Discuss in Forum

    The given sequence is based on the following pattern :
    First term = 2
    Second term = First term + 4 = 2 + 4 = 6
    Third term = Second term + 6 = 6 + 6 = 12
    Fourth term = Third term + 8 = 12 + 8 = 20
    Fifth term = Fourth term + 10 = 20 + 10 = 30
    Sixth term = Fifth term + 12= 30 + 12 = 42
    ........... and so on.

    Correct Option: D

    The given sequence is based on the following pattern :
    First term = 2
    Second term = First term + 4 = 2 + 4 = 6
    Third term = Second term + 6 = 6 + 6 = 12
    Fourth term = Third term + 8 = 12 + 8 = 20
    Fifth term = Fourth term + 10 = 20 + 10 = 30
    Sixth term = Fifth term + 12= 30 + 12 = 42
    Seventh term = Sixth term + 14= 42 + 14 = 56
    Eight term = Seventh term + 16= 56 + 16 = ?
    ∴ ? = 72

    ∴ Required number = 72


  1. Which number in the sequence 8, 27, 64,100, 125, 216, 343 is wrongly written?









  1. View Hint View Answer Discuss in Forum

    In the given sequence all the numbers except 100 are perfect cubes of natural numbers.
    As, 8 = 2³,
    27 = 3³,
    64 = 4³
    100 = 10² ≠ 10³
    ........... and so on.

    Correct Option: B

    In the given sequence all the numbers except 100 are perfect cubes of natural numbers.
    As, 8 = 2³,
    27 = 3³,
    64 = 4³
    100 = 10² ≠ 10³
    125 = 5³
    Hence , the wrong term is 100.



  1. The value of x in the sequence 1, 2, 6, 24, x is









  1. View Hint View Answer Discuss in Forum

    The given sequence is based on the following pattern :
    First term = 1
    Second term = First term × 2 = 1 × 2 = 2
    Third term = Second term × 3 = 2 × 3 = 6
    Fourth term = Third term × 4 = 6 × 4 = 24
    Fifth term = Fourth term × 5 = 24 × 5 = ?
    ........... and so on.

    Correct Option: D

    The given sequence is based on the following pattern :
    First term = 1
    Second term = First term × 2 = 1 × 2 = 2
    Third term = Second term × 3 = 2 × 3 = 6
    Fourth term = Third term × 4 = 6 × 4 = 24
    Fifth term = Fourth term × 5 = 24 × 5 = ?
    ∴ ? = 120

    Hence, 120 will replace x.


  1. The value of in the sequence 27, 9, 3 , ? ,
    1
    ,
    1
    ,
    1
    is :
    3927










  1. View Hint View Answer Discuss in Forum

    The given sequence is based on the following pattern :
    First term = 27
    Second term = First term ÷ 3 = 27 ÷ 3 = 9
    Third term = Second term ÷ 3 = 9 ÷ 3 = 3
    Fourth term = Third term ÷ 3 = 3 ÷ 3 = ?
    ∴ ? = 1
    ........... and so on.

    Correct Option: B

    The given sequence is based on the following pattern :
    First term = 27
    Second term = First term ÷ 3 = 27 ÷ 3 = 9
    Third term = Second term ÷ 3 = 9 ÷ 3 = 3
    Fourth term = Third term ÷ 3 = 3 ÷ 3 = ?
    ∴ ? = 1

    Fifth term = Fourth term ÷ 3 =
    1
    3

    Sixth term = Fifth term ×
    1
    =
    1
    39

    ........... and so on.

    Hence , The value of ? is 1.



  1. The numbers of the sequence 56, 72, 90,110, 132, 154, form a pattern. Which of them is a misfit in the pattern?









  1. View Hint View Answer Discuss in Forum

    The given sequence is based on the following pattern :
    7 × 8 = 56
    8 × 9 = 72
    9 × 10 = 90
    10 × 11 = 110
    11 × 12 = 132
    12 × 13 ≠ 154

    Correct Option: D

    The given sequence is based on the following pattern :
    7 × 8 = 56
    8 × 9 = 72
    9 × 10 = 90
    10 × 11 = 110
    11 × 12 = 132
    12 × 13 ≠ 154, Since 154 is wrong term . so , 156 will be correct term.
    ∴ 154 is the wrong number.