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50 - Digit Number (Posted on 2003-11-15) Difficulty: 3 of 5
A number of 50 digits has all its digits equal to 1 except the 26th digit. If the number is divisible by 13, then find the digit in the 26th place.

See The Solution Submitted by Ravi Raja    
Rating: 3.3333 (6 votes)

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A similar problem but perhaps a bit trickier | Comment 12 of 39 |
Hi.
I'm new here, so please forgive me for posting this if I'm not supposed to, but I like this kind of problem. The technique to the problem is handy to remember in maths challenges...
The problem is this:

A student realises that a certain 12-digit number is exactly divisible by 11. His mate comes along and drops ink over the 8th digit. The student can now only read 11 of the 12 digits and cannot remember what the "inked" digit was. Can you work it out? The number now reads:
5643879x2841. (Where 'x' is the number blotted out with ink)


  Posted by Kirk on 2003-11-20 14:53:01
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