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#1 2020-04-11 09:31:15

Nasir Hassan
Member
Registered: 2020-04-11
Posts: 6

9-Digit Number Puzzle

Your solution is 473816952.  However, the question states that rounding is done alternatively - up, down, up ....  With 2 as the units digit, the 1st rounding will be down, not up.

My solution is 536192748. It's divisible by 6 and 7, and the alternative rounding starting from up then down etc  gives 53619 0000, with digits adding up to24.  Where's the flaw in this answer?  Unless the number 4 becomes 5 after the 1st round up, and the number 7 does't round down to 7 because of the 5?

Regards

Nasir

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#2 2020-04-11 20:09:28

Bob
Registered: 2010-06-20
Posts: 10,512

Re: 9-Digit Number Puzzle

hi Nasir Hassan

Welcome to the forum.

I agree that your solution is better.  The one given would be ok if the question read "it rounds in an alternate pattern (down, up, down ...).  I don't have any editorial control over the MIF site so I'll message the boss and suggest a re-write.

Best wishes, stay safe,

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

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#3 2020-04-19 12:59:53

MathsIsFun
Registered: 2005-01-21
Posts: 7,713

Re: 9-Digit Number Puzzle

Your solution is right Nasir, thank you!

And Bob is right, the old solution (473816952) works when the rounding starts at down, then up, etc

Will amend.

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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#4 2020-04-19 13:17:52

MathsIsFun
Registered: 2005-01-21
Posts: 7,713

Re: 9-Digit Number Puzzle

Here is the amended puzzle:

https://www.mathsisfun.com/puzzles/9-digit-number-solution.html