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 , 3 , 11 , 38 ,102 , 229 , 443











  1. View Hint View Answer Discuss in Forum

    The given series is in the below pattern,
    First term = 2
    Second term = First term + 13 = 3
    Third term = Second term + 23 = 11
    Similarly , we can calculate all others terms also.

    Correct Option: B

    The given series is in the below pattern,
    First term = 2
    Second term = First term + 13
    Second term = 2 + 13 = 3 ;
    Third term = Second term + 23
    Third term = 3 + 23 = 11 ;
    Similarly , we can find the all others terms also.
    Fourth term = Third term + 42
    Fourth term = 11 + 33 = 38 ;
    Fifth term = Fourth term + 52
    Fifth term = 38 + 43 = 102
    Sixth term = Fifth term + 62
    Sixth term = 102 + 53 = 229 ; 229 is wrong. It should be 227.
    Seventh term = Sixth term + 72
    Seventh term = 227 + 63 = 443
    Hence, 229 is wrong. It should be 227.






  1. 2807, 1400, 697, 347, 171, 84, 41, 20











  1. View Hint View Answer Discuss in Forum

    From the given figure , we can see that
    First term = 2807
    Second term = ( First term - 7 ) ÷ 2 = 1400
    Third term = ( Second term - 6 ) ÷ 2 = 697

    Correct Option: B

    From the given figure , we can see that
    First term = 2807
    Second term = ( First term - 7 ) ÷ 2 = 1400
    Third term = ( Second term - 6 ) ÷ 2 = 697
    Second term = ( 2807 - 7 ) ÷ 2 = 1400 ;
    Third term = ( 1400 - 6 ) ÷ 2 = 697 ;
    Fourth term = ( 697 - 5 ) ÷ 2 = 347; 347 is wrong. It should be 346.
    Fifth term = ( 346 - 4 ) ÷ 2 = 171 ;
    Sixth term = ( 171 - 3 ) ÷ 2 = 84 ;
    Seventh term = ( 84 - 2 ) ÷ 2 = 41 ;
    Eighth term = ( 41 - 1 ) ÷ 2 = 20
    Hence, 347 is wrong. It should be 346.




  1. 2 , 3 , 5 , 8 , 14 , 23 , 41, 69











  1. View Hint View Answer Discuss in Forum

    The series is an alternate series, having
    Next term = ( Previous term × 3 ) - 1
    Odd position series :-
    First term = 2
    Third term = ( First term × 3 ) - 1
    .........................and so on .
    Even position series :-
    Second term = 3
    Fourth term = ( Second term × 3 ) - 1
    .........................and so on .

    Correct Option: E

    The series is an alternate series, having
    Odd position series :-
    First term = 2
    Third term = ( First term × 3 ) - 1
    Third term = ( 2 × 3 ) - 1 = 5 ;
    Fifth term = ( Third term × 3 ) - 1
    Fifth term = ( 5 × 3 ) - 1 = 14 ;
    Seventh term = ( Fifth term × 3 ) - 1
    Seventh term = ( 14 × 3 ) - 1 = 41 ;
    Even position series :-
    Second term = 3
    Fourth term = ( Second term × 3 ) - 1
    Fourth term = ( 3 × 3 ) - 1 = 8 ;
    Sixth term = ( Fourth term × 3 ) - 1
    Sixth term = ( 8 × 3 ) - 1 = 23 ;
    Eighth term = ( Sixth term × 3 ) - 1
    Eighth term = ( 23 × 3 ) - 1 = 69; 69 is wrong. It should be 68.


  1. 3 , 7. 5 ,15 , 37.5 , 75 ,167.5 , 375











  1. View Hint View Answer Discuss in Forum

    The given series is in the below pattern,
    First term = 3
    Second term = First term × 2.5 = 7.5 ;
    Third term = Second term × 2 = 15 ;
    Similarly , we can calculate all others terms also.

    Correct Option: A

    The given series is in the below pattern,
    First term = 3
    Second term = First term × 2.5
    Second term = 3 × 2.5 = 7.5 ;
    Third term = Second term × 2
    Third term = 7.5 × 2 = 15 ;
    Fourth term = Third term × 2.5
    Fourth term = 15 × 2.5 = 37.5 ;
    Fifth term = Fourth term × 2
    Fifth term = 37.5 × 2 = 75 ;
    Sixth term = Fifth term × 2.5
    Sixth term = 75 × 2.5 = 167.5; 167.5 is wrong. It should be 187.5.
    Seventh term = Sixth term × 2
    Seventh term = 187.5 × 2 = 375 ;
    Hence, 167.5 is wrong. It should be 187.5.



  1. 36 , 20 , 12 , 8 , 6 , 5.5 , 4.5











  1. View Hint View Answer Discuss in Forum

    The given series is in the below pattern,we can see that
    Difference between all terms are given as :- 16 ÷ 2 = 8 , 8 ÷ 2 = 4 , 4 ÷ 2 = 2 , 2 ÷ 2 = 1 , 1 ÷ 2 = 0.5 .
    First term = 36
    Second term = First term - 16 = 20 ;
    Third term = Second term - 8 = 12 ;
    Similarly , we can calculate all next terms also.

    Correct Option: A

    As per given above series , it is clear that
    Difference between all terms are given as :- 16 ÷ 2 = 8 , 8 ÷ 2 = 4 , 4 ÷ 2 = 2 , 2 ÷ 2 = 1 , 1 ÷ 2 = 0.5 .
    First term = 36
    Second term = First term - 16
    Second term = 36 - 16 = 20 ;
    Third term = Second term - 8
    Third term = 20 - 8 = 12 ;
    Similarly , we can find all others terms also.
    Fourth term = Third term - 4 = 12 - 4 = 8 ;
    Fifth term = Fourth term - 2 = 8 - 2 = 6 ;
    Sixth term = Fifth term - 1 = 6 - 1 = 5.5; 5.5 is wrong. It should be 5 .
    Seventh term = Sixth term - 0.5 = 5 - 0.5 = 4.5
    Hence, 5.5 is wrong. It should be 5 as Sixth term .