# Thread: Missing number in the series

1. ## Missing number in the series

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

2. ## 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  Reply With Quote

3. ## Re: Missing number in the series

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

4. ## Re: Missing number in the series Originally Posted by scott 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  Reply With Quote

5. ## Re: Missing number in the series

yep

current No - (90 + 5)

Prev No - 90

so 90 + 95 = 185  Reply With Quote

6. ## Missing number in the series Originally Posted by scott What is the missing number in the series?
4,9,20,43,90??
the next no of the series is 143  Reply With Quote

7. ## Missing number in the series Originally Posted by scott What is the missing number in the series?
4,9,20,43,90??
the last no of the series is 143  Reply With Quote

8. ## 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.  Reply With Quote

9. ## 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  Reply With Quote

10. ## Re: Missing number in the series Originally Posted by scott What is the missing number in the series?
4,9,20,43,90??  Reply With Quote

11. ## Re: Missing number in the series  Reply With Quote

12. ## Re: Missing number in the series  Reply With Quote

13. ## Re: Missing number in the series

How can I draw up a formula that number series?

4,9,20,43,90??
Thank you!  Reply With Quote

14. ## 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  Reply With Quote

15. ## 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  Reply With Quote

16. ## 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  Reply With Quote

17.

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