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 50 - Digit Number (Posted on 2003-11-15)
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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 Less thinking using extended precision | Comment 3 of 39 |
(In reply to solution by Charlie)

The mod-13 values could be found directly via extended precision provided by UBASIC:

```
list

10   point 15

20   for I=0 to 49

30     N=N+10^I

40   next

50   print N@13

60   print (10^24)@13

OK

run

11

1

OK

telling us the original mod value and the mod value

for each additional point in the 26th position, then:

? 11111111111111111111111113111111111111111111111111 @ 13

0

OK

```

---------
With the latter immediate-mode print command (the ?) being a check on the answer.

 Posted by Charlie on 2003-11-15 11:46:40

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