perplexus.info :: Numbers : Move the 2

Move the 2 - double the number (Posted on 2002-04-19)

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.)

The continued fraction way

| Comment 6 of 10 |

We are looking for a number abcde...z2.

Let's consider the continued fraction n=0.abcde...z2abcde...z2...

It follows that n/10+0.2 = 0.2abcde...z2abcde...z2... = 2n as stated, and we get n=2/19=0.105263157894736842.

Posted by Federico Kereki on 2003-12-04 09:49:37

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