perplexus.info :: Just Math : Lucky seven V

Lucky seven V (Posted on 2011-09-13)

A base ten number formed by writing the digit seven precisely 2011 times is denoted by N. That is:

N = 77ЕЕ77 (2011 times).

Let us denote x = [N/9], y = [x/9] and, z = [y/9]

Determine the digital root of z.

Note: [P] denotes the greatest integer ≤ P

**** For an extra challenge, solve this puzzle without using a computer program.

Submitted by K Sengupta

Rating: 5.0000 (1 votes)

Solution: (Hide)

The digital root of z is 6.
For an explanation, refer to the analytic solution submitted by Brian Smith in this location.
You can also refer to the computer assisted solution submitted by Charlie in this location for purposes of verification.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
Solution	Brian Smith	2016-12-23 15:53:10
Outline of non-computer solution	Jer	2011-09-14 11:03:47
computer solution	Charlie	2011-09-13 13:41:33

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