Life In 19x19

Describe the next figure in this array. How long did it take you?

congratulations both. Both very fast. Easy for go players???

Next puzzle:
You have 2 lenghts of fuse and 2 matches. One fuse will burn from start to end in 10 minutes. The other in 15 minutes. However the burn rate is not steady along their lenghts. Measure 20 minutes of time.

( for the not native english: a fuse is the sort of rope they used to ignite bombs in the good old days, also used in fireworks. It has nothing to do with electricity OC )

Fuses

cyclops wrote:congratulations both. Both very fast. Easy for go players???

Who knows? It might be hard for go players. After all, solving it demands breaking down the gestalts. That might be difficult for a whole board thinker.

Fuses:

I'm dumb enough not to get the first one, and have suppressed my shame enough to admit it. Even after reading the answers, I can't see why it would be that way. Explanation?

amnal wrote:

hyperpape wrote:I'm dumb enough not to get the first one, and have suppressed my shame enough to admit it. Even after reading the answers, I can't see why it would be that way. Explanation?

Cover up the left half of each symbol

hyperpape, I'm with you.

@amnal

Both answers correct for the fuses problem. Next problem.

on a strange island there lives a strange tribe of 300 perfectly logical and perfectly intelligent persons. And they know it of each other. Each member has a spot, red or black, on the back of the head. Nobody knows the color of his own spot but they do know the color of everybody else's. If a tribesman ever realizes the color of his own spot it is strict custom that he publicly announces this fact the next morning and leaves the island forever. So they never mention spot colors and have no mirrors. But one day a tourist, American OC, visits the island and announces to the entire tribe: "I can see at least one of you has a red spot!". The tourist leaves to return a year later.
He is surprised. Why?