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 Building a ruler (Posted on 2008-11-14)
I have an unmarked ruler (AD) of length 6cm. Making two marks in it, one (B) at 1cm from the left end and other (C) at 2cm from the right end, I´m able to measure any integer length from 1 to 6 cm:
```       +----+-------------+--------+
A    B             C        D```
AB = 1cm / CD = 2cm / BC = 3cm / AC = 4cm / BD = 5cm / AD = 6cm.

If I have an unmarked ruler of length 14cm, what is the minimum number of marks, and where do I have to make them, in order to be able to measure any integer length from 1 to 14cm?

 See The Solution Submitted by pcbouhid No Rating

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 re: Catch? | Comment 3 of 10 |
(In reply to Catch? by ed bottemiller)

As you pointed out it's easy to see there's more than one solution, thus rather than focusing on "the" solution, a solver might provide one such solution.

However, I think the main point is to prove you can't do it with 4 or fewer marks, since there's theoretically 15 distances. (Also keep in mind this is D2, so it's unlikely the solution is anything difficult)

 Posted by Gamer on 2008-11-14 18:33:08

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