Another puzzle...

Jim isn't the only one who can post trick questions here. This is an old one, so if you've seen it before, let the others think for a while before replying...

You have nine dots on a paper, as seen below. Your task is to connect them with four straight lines without lifting the pencil:

o o o
o o o
o o o

.... and when you're done with that: Tell me how to do it with *one* straight line...

/Claes

The firewall here won't let me post an attachment, so try to follow this

1 2 3 10

4 5 6

7 8 9

11

9-5-1, 1-2-3 and extend to 10, 6-8 and extend to 11, 7-4 and done.

Thinking outside the box

I agree with KenS. Took a moment to figure out what he was doing, but good idea to replace the dots with numbers as an explanation!

As for *one* line, Claes, I sugges a very thick marker that will cover up all three columns at once. Or does it have to be a straight line?....would a circular line be allowed?

Yep

Yep, a thick marker would do it with one line. However, there is at least one more way...

/Claes

One Straight Line

Refering to my earlier post, a spiral following the path

1-3-9-7-2-6-8-4 then a straight line to 5. Only *one* straight line.

Re: One Straight Line

KenS said:

Refering to my earlier post, a spiral following the path

1-3-9-7-2-6-8-4 then a straight line to 5. Only *one* straight line.

Click to expand...

Clever... KenS is clearly thinking outside our normal references... Which is what you have to do here. But it can be done with a straight line. Without the spiral...

/Claes

This might sound stupid, or it might violate Claes' rules, but here goes...

I'm assuming a straight line can be drawn around a sphere (like the equator on a globe) and it is still considered a straight line (logical???). Hold the paper with the 9 dots on it so that 1,2,3 are on the "equator" at the front of the globe and draw the line, then, while the line is being re-traced around the back of the globe, move the paper so that 4,5,6, are on the equator and they get marked on the next pass of the pencil around the equator. Repeat for 7,8,9. The pencil never leaves the globe, but the line is re-traced 3 times. Only the paper moves.

Could do the same thing on a flat table if you are allowed to stop the pencil -- just re-trace the straight line back and forth as the paper with the dots moves.

Okay, shoot.

Bending the rules

Another clever way.. Not bad. Actually the trick here is to bend the rules a bit. I guess that's part of thinking outside the normal references.

I think you could go around the globe and connect the dots without moving the paper: Even the tiniest dot is more than big enough to allow for the slight angle deviation enabling the line to hit the next row of dots...

I was thinking of simply folding the paper into a tube and doing the same thing... which would save a bit of time.

Ok... Now: 3 lines....?

/Claes

Long overdue...

Here is one way to do it with three lines:



/Claes

Claes Gefvenberg said:

Another clever way.. Not bad. Actually the trick here is to bend the rules a bit. /Claes

Click to expand...

Captain Kirk strikes again. . . the Kobiyashi Maru scenario. . . change (bend) the rules!