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Thread: Missing number in the series

  1. #1
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    Missing number in the series

    What is the missing number in the series?
    4,9,20,43,90??


  2. #2
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    Re: Missing number in the series

    Ans: 185.

    diff between 4 and 9 is 5 (4+1)
    diff between 9 and 20 is 11 (9+2)
    diff between 20 and 43 is 23 (20+3)
    diff between 43 and 90 is 47(43+4)


    -- James


  3. #3
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    Re: Missing number in the series

    James your approach is prefect and the solution for this problem is 185 as you found out.


  4. #4
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    Re: Missing number in the series

    Quote Originally Posted by scott View Post
    What is the missing number in the series?
    4,9,20,43,90??
    Another approach

    (4*2) + 1 = 9
    (9*2) + 2 = 20
    (20*2) + 3 = 43
    (43*2) + 4 = 90
    (90*2) + 5 = 185


  5. #5
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    Re: Missing number in the series

    yep

    current No - (90 + 5)

    Prev No - 90

    so 90 + 95 = 185


  6. #6
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    Missing number in the series

    Quote Originally Posted by scott View Post
    What is the missing number in the series?
    4,9,20,43,90??
    the next no of the series is 143

    Last edited by sadaf; 05-14-2009 at 07:35 AM.

  7. #7
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    Missing number in the series

    Quote Originally Posted by scott View Post
    What is the missing number in the series?
    4,9,20,43,90??
    the last no of the series is 143


  8. #8
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    Cool Re: Missing number in the series

    4 9 20 43 90 ?

    the difference

    4 9 20 43 90 ?

    5 11 23 47 ?

    6 12 24 48

    so the 3rd series is 6 12 24 (48) it doubles the digit.. adding 48 in 47 so the figure is 95 now we got main difference series.....adding 95 in main series 90 then ans is 185.


  9. #9
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    Re: Missing number in the series

    Hi,

    The missing number is 185.

    Here is the explanation

    4 9 20 43 90

    9-4=5
    20-9=11
    43-20=23
    90-43=47

    (5*2)+1=11
    (11*2)+1=23
    (23*2)+1=47

    so, in the same way (47*2)+1=95

    So, x-95=90.

    Therefore x= 185.

    Thanks


  10. #10

    Smile Re: Missing number in the series

    Quote Originally Posted by scott View Post
    What is the missing number in the series?
    4,9,20,43,90??
    please find the steps


  11. #11

    Re: Missing number in the series

    answer is 186


  12. #12

    Re: Missing number in the series

    answer is 186&379


  13. #13
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    Re: Missing number in the series

    How can I draw up a formula that number series?

    4,9,20,43,90??
    Thank you!


  14. #14
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    Re: Missing number in the series

    Hi Isabele,

    The formula is defined as
    The difference between 9-4= 4+1 is 5
    20-9=(5+5)+1 is 11
    43-20=(11+11)+1 is 23
    90-43=(23+23)+1 is 47
    185-90=(47+47)+1 is 95
    so the answer is 90+95(add last number+difference number) = 185


  15. #15
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    6

    Re: Missing number in the series

    4 + 4 + 1 = 9
    9 + 9 + 2 = 20
    20 + 20 + 3 = 43
    43 + 43 + 4 = 90
    90 + 90 + 5 = 185


  16. #16
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    Re: Missing number in the series

    185
    In this series each 2nd no is incremented by 1 with double of the previous number.
    9=4*2+1
    20=9*2+2
    43=20*2+3
    90=43*2+4
    so, next number will be 185 as
    185=90*2+5


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