Number Series


Direction: In each of these questions a number series is given. Only one number is wrong in each series. You have to find out the wrong number.

  1. 2 , 8 ,32 , 148 , 765 , 4626 , 32431
    1. 765
    2. 148
    3. 8
    4. 32
    5. 4626

  1. View Hint View Answer Discuss in Forum

    From the given graph , we can see that the increasing order of series as -
    First term = 2
    Second term = First term + 22 = 8
    Third term = Second term + 32 = 32
    Similarly , we can calculate all others terms also.

    Correct Option: D

    From the given graph , we can see that the increasing order of series as -
    First term = 2
    Second term = First term × 2 + 22
    Second term = 2 × 2 + 22 = 4 + 4 = 8 ;
    Third term = Second term × 3 + 32
    Third term = 8 × 3 + 32 = 24 + 9 = 32 ; 32 is wrong. It should be 33.
    Similarly , we can find all others terms also.
    Fourth term = Third term × 4 + 42
    Fourth term = 33 × 4 + 42 = 132 + 16 = 148 ;
    Fifth term = Fourth term × 5 + 52
    Fifth term = 148 × 5 + 52 = 740 + 25 = 765 ;
    Sixth term = Fifth term × 6 + 62
    Sixth term = 765 × 6 + 62 = 4590 + 36 = 4626 ;
    Seventh term = Sixth term × 7 + 72
    Seventh term = 4626 × 7 + 72 = 32382 + 49 = 32431
    Hence, 32 is wrong. It should be 33.



  1. 108 , 54 , 36 ,18 , 9 , 6 , 4
    1. 54
    2. 36
    3. 18
    4. 9
    5. 6

  1. View Hint View Answer Discuss in Forum

    The given series is in the below pattern,we can see that
    Next term = Previous term ÷ n { putting n = 2 and 1.5 alternately }
    First term = 108
    Second term = First term ÷ 2
    Second term = 108 ÷ 2 = 54 ;
    Third term = Second term ÷ 1.5
    Third term = 54 ÷ 1.5 = 36 ;
    Similarly , we can calculate all others terms also.

    Correct Option: D

    The given series is in the below pattern,we can see that
    Next term = Previous term ÷ n { putting n = 2 and 1.5 alternately }
    First term = 108
    Second term = First term ÷ 2
    Second term = 108 ÷ 2 = 54 ;
    Third term = Second term ÷ 1.5
    Third term = 54 ÷ 1.5 = 36 ;
    Third term = Third term ÷ 2
    Fourth term = 36 ÷ 2 = 18 ;
    Fifth term = Fourth term ÷ 1.5
    Fifth term = 18 ÷ 1.5 = 9 is wrong. It should be 12.
    Sixth term = Fifth term ÷ 2
    Sixth term = 12 ÷ 2 = 6 ;
    Seventh term = Sixth term ÷ 1.5
    Seventh term = 8 ÷ 1.5 = 4
    Hence, 9 is wrong. It should be 12.



  1. 0 , 1 , 9 , 36 , 99 , 225 , 441
    1. 9
    2. 36
    3. 99
    4. 225
    5. 441

  1. View Hint View Answer Discuss in Forum

    From above given series , we can see that
    The differences are given as -
    Second term - First term = 1– 0 = 1 = 13;
    Third term - Second term = 9 – 1= 8 = 23;
    Similarly , we can calculate all others terms also.

    Correct Option: C

    From above given series , we can see that
    The differences are given as -
    Second term - First term = 1– 0 = 1 = 13;
    Third term - Second term = 9 – 1= 8 = 23;
    Similarly , we can find all others terms also.
    Fourth term - Third term = 36 – 9 = 27 = 33;
    Fifth term - Fourth term = 99 – 36 = 63 ≠ 4 3
    But , Fifth term - Fourth term = 100 – 36 = 64 = 43;
    Here , fifth term 99 is wrong , it should be 100 as fifth term .
    Sixth term - Fifth term = 225 – 100 = 125 = 53;
    Seventh term - Sixth term = 441– 225 = 216 = 63


  1. 2 , 3 , 6 , 15 , 45 , 156.5 , 630
    1. 3
    2. 45
    3. 15
    4. 6
    5. 156.5

  1. View Hint View Answer Discuss in Forum

    As per the details in the question the series is in the form of
    First term = 2
    Second term = First term × 1.5 = 3
    Third term = Second term × 2 = 6
    Similarly , we can calculate all next terms also.

    Correct Option: E

    As per the details in the question the series is in the form of
    First term = 2
    Second term = First term × 1.5
    Second term = 2 × 1.5 = 3 ;
    Third term = Second term × 2
    Third term = 3 × 2 = 6 ;
    Similarly , we can find all others terms also.
    Fourth term = Third term × 2.5 = 6 × 2.5 = 15 ;
    Fifth term = Fourth term × 3 = 15 × 3 = 45 ;
    Sixth term = Fifth term × 3.5 = 45 × 3.5 =156.5; 156.5 is wrong. It should be 157.5 .
    Seventh term = Sixth term × 4 =157.5 × 4 = 630
    Hence, 156.5 is wrong. It should be 157.5.



  1. 5 , 8 ,16 , 26 , 50 , 98 ,194
    1. 8
    2. 26
    3. 50
    4. 16
    5. 98

  1. View Hint View Answer Discuss in Forum

    The given series is in the below pattern,
    Next term = ( Previous term × 2 ) - 2
    First term = 5
    Second term = ( First term × 2 ) - 2 = 8 ;
    Third term = ( Second term × 2 ) - 2 = 16 ;
    Similarly , we can calculate all others terms also.

    Correct Option: D

    The given series is in the below pattern,
    Next term = ( Previous term × 2 ) - 2
    First term = 5
    Second term = ( First term × 2 ) - 2
    Second term = ( 5 × 2 ) - 2 = 8 ;
    Third term = ( Second term × 2 ) - 2
    Third term = ( 8 × 2 ) - 2 = 16; 16 is wrong. It should be 14.
    Similarly , we can calculate all others terms also.
    Fourth term = ( Third term × 2 ) - 2
    Fourth term = ( 14 × 2 ) - 2 = 26 ;
    Fifth term = ( Fourth term × 2 ) - 2
    Fifth term = ( 26 × 2 ) - 2 = 50 ;
    Sixth term = ( Third term × 2 ) - 2
    Sixth term = ( 50 × 2 ) - 2 = 98 ;
    Seventh term = ( Sixth term × 2 ) - 2
    Seventh term = ( 98 × 2 ) - 2 = 194
    Hence, 16 is wrong. It should be 14.