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Move the 2 - double the number (Posted on 2002-04-19) Difficulty: 3 of 5
A certain number ends with the digit 2. Moving the 2 from the end of the number to its front doubles it. Can you find this number?

(Hint: it's quite large)

See The Solution Submitted by levik    
Rating: 4.1111 (9 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
another method | Comment 4 of 10 |
This can be approached as a division problem, and thereby proceed from left to right, and it seems as easy as the multiplication approach:


1
2)2

so place a 1 to the right in the dividend:

1
2)21
2
01

requiring a zero in the quotient, and also to the right in the dividend, and brought down:

10
2)210
2
010

leading to a 5 in the quotient and dividend:

105
2)2105
2
010
10
05

leading to a 2, etc.

until eventually a 04 (not a 05) appears at the bottom that has to be divided by 2, so a 2 can be placed at the rightmost portion and zero out the bottom subtraction.
  Posted by Charlie on 2003-06-04 04:01:16
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