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# Maths Problem watch

1. (Original post by elpaw)
*cough* 198 *cough*
But if 89 = 10b + c how is b = 9?
2. (Original post by elpaw)
you're not going to even get into QM
Thanks for your support (!), I'll go and see if UEL have a place for me...
3. (Original post by ZJuwelH)
But if 89 = 10b + c how is b = 9?
its not, 89 = b + 10c
4. (Original post by ZJuwelH)
But if 89 = 10b + c how is b = 9?
Because it's 10c +b
5. (Original post by ZJuwelH)
Thanks for your support (!), I'll go and see if UEL have a place for me...
i wouldn't even bother going to the exam hall.....
6. (Original post by elpaw)
i wouldn't even bother going to the exam hall.....
lol
7. (Original post by mikesgt2)
198 is the only one

4 digit numbers gives:

989a + 89b = 10d + c

Which is impossible for a,b,c,d < 10 because max of 10d + c is 99 but the minimum of the lhs is 989 because a has to be at least 1
And 5 digit numbers? 6,7,8?
8. (Original post by theone)
And 5 digit numbers? 6,7,8?
do you have to use some sort of proof by induction?
9. <sits in corner of infant school classroom and sobs> Leave me alone!

Bloody football result messed my brain up. There's new champions on the block and they play in blue...
10. (Original post by elpaw)
do you have to use some sort of proof by induction?
Would be easier than going all the way to infinity-digit numbers...
11. (Original post by elpaw)
do you have to use some sort of proof by induction?
You can but don't really have to...
12. (Original post by theone)
You can but don't really have to...
9989a + 989b + 89c = d +10e

Since least no. for rhs is 9989 when a is 1. it would be impossible, as d +10e can only go up to 99.
13. (Original post by 2776)
9989a + 989b + 89c = d +10e

Since least no. for rhs is 9989 when a is 1. it would be impossible, as d +10e can only go up to 99.
what about k digit numbers, where k > 5
14. (Original post by theone)
what about k digit numbers, where k > 5
15. (Original post by theone)
what about k digit numbers, where k > 5
Surely u can't go any further. Because u will always meet 10a + b for the lhs. And where (k-1)9's89 is the minimum, so you will never get another answer, surely?
16. (Original post by 2776)
Surely u can't go any further. Because u will always meet 10a + b for the lhs. And where (k-1)9's89 is the minimum, so you will never get another answer, surely?
not rigorous enough for the rep
17. (Original post by theone)
not rigorous enough for the rep
tell me which part is not rigerous enough
18. (Original post by 2776)
9989a + 989b + 89c = d +10e

Since least no. for rhs is 9989 when a is 1. it would be impossible, as d +10e can only go up to 99.
((10^n)a-11)+((10^(n-1))b-11)...((10^2)z) = m+10n

Since smallest possibility of LHS is ((10^n)a-11) it's impossible as m+10n only returns 99 at best...

Really babyish I think but...
19. (Original post by ZJuwelH)
((10^n)a-11)+((10^(n-1))b-11)...((10^2)z) = m+10n

Since smallest possibility of LHS is ((10^n)a-11) it's impossible as m+10n only returns 99 at best...

Really babyish I think but...
That'll do, although i was thinking of a nicer method imho.
20. (Original post by theone)
That'll do, although i was thinking of a nicer method imho.

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