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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 5 of 10 |
(In reply to Catch? by ed bottemiller)

Though Charlie's analysis is probably the correct and sought after by the poser, there could be a trick solution by interpreting the 14 cm ruler as an additional ruler:

3 marks; a 1 cm mark from one edge and a 4 cm mark from the other edge of the 14 cm and a 2 cm mark from one edge of the 6 cm ruler.  Using the combination of rulers and their marks, all integer lengths from 1 cm to 14 cm can be measured.

 Posted by Dej Mar on 2008-11-14 23:48:22

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