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# 9-digit Number

18 replies to this topic

### #1 rookie1ja

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Posted 30 March 2007 - 07:34 PM

9-digit Number - Back to the Number Puzzles
Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not rounded numerals equals 24.

This old topic is locked since it was answered many times. You can check solution in the Spoiler below.
Pls visit New Puzzles section to see always fresh brain teasers.

Spoiler for Solution

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### #2 brain_bashed25

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Posted 03 July 2007 - 12:44 AM

I dont think my head can go that far. im Guessing the number 123456789
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### #3 asalsv

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Posted 11 July 2007 - 06:57 PM

your solution does not make sense based on the criteria you gave. Could you explain how you came up with your solution please.

in your number, you did not alternate rounding up and down and you rounded the last number which in your directions you said not to do and after your fourth time rounding, the remaining numbers add up to 23 not 24.

I hope you can explain your solution, because I am very confused at this point as i had a very different solution.

thank you
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### #4 savagegamer90

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Posted 11 July 2007 - 07:04 PM

the numbers work 473816952 you still round up for the first one, down for the second one, up for the third one and so on, then the numbers add up to 24 and it works
2 rounds down to zero, 5 stays the same
5 rounds up to zero, 9 adds one becomes 0
0 rounds down zero, 6 stays a six
6 rounds up to zero, 1 adds one becomes 2
2+8+3+7+4 =24
finish rounding numbers and you end up with
500000000
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Posted 11 August 2007 - 08:40 PM

I came up with another answer. The problem says "The rounding alternates (up, down, up ...)" so I started rounding up, not down first. Here is what I came up with, I believe it meets all the criteria of the problem:

518372946

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### #6 peachykeen

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Posted 21 August 2007 - 08:33 PM

Is there any other way to do this besides trial and error?
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### #7 peachykeen

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Posted 21 August 2007 - 08:34 PM

[

I came up with another answer. The problem says "The rounding alternates (up, down, up ...)" so I started rounding up, not down first. Here is what I came up with, I believe it meets all the criteria of the problem:

518372946

follow:
5183729846 -- round up
5183729850 -- round up again!
5183729900 -- and we round up again...and so forth.

I think you probably just missed that 4 going up to a 5 since it would alternate other than that!
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### #8 derktheturk

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Posted 22 September 2007 - 05:31 PM

I came up with another answer. The problem says "The rounding alternates (up, down, up ...)" so I started rounding up, not down first. Here is what I came up with, I believe it meets all the criteria of the problem:

518372946

Perhaps Adam begins on the incorrect end. Instructions indicate one is to begin with the units, then 10's and so-on. Otherwise, he would be correct.
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### #9 BoilingOil

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Posted 26 September 2007 - 06:09 PM

your solution does not make sense based on the criteria you gave. Could you explain how you came up with your solution please.

in your number, you did not alternate rounding up and down and you rounded the last number which in your directions you said not to do and after your fourth time rounding, the remaining numbers add up to 23 not 24.

I hope you can explain your solution, because I am very confused at this point as i had a very different solution.

thank you

You make one mistake here: after the forth rounding (up), the 1 would have become a 2, and the sum of the remaining numbers would then INDEED be 24!
This was an easy onion to peel.

BoilingOil
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### #10 Puzzlerz

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Posted 04 December 2007 - 12:56 AM

Since you have an error in your conditions (the sum of the remaining numerals after 4 round-offs in your answer is NOT 24 as you stipulate--yours is 23) and with only 8 round-offs starting with rounding up, the last round-off has to be down, your answer is incorrect. I believe my answer is, therefore, equally valid. My 9-digit number is: 546372819
First rounding (up) yields: 546372820
2nd rounding (dn) yields: 546372800
3rd rounding (up) yields: 546373000
4th rounding (dn):546370000
5th rounding (up): 546400000
6th rounding (dn): 546000000
7th rounding (up): 550000000
8th rounding (dn): 500000000

Thanks for the challenge.
Linda, the Puzzlerz
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