18 matchsticks aka 18 nails aka 18 toothpicks

It’s a while ago we had matchstick puzzles, so here’s one again. And yes, you are perfectly right, matches are on the way out with electric cooking and all such. Luckily, you can use nails or toothpick sticks instead. I mentioned it in a previous post and I’m now also mentioning it in the title of the post.

In the image below you see 18 matchsticks aka nails aka toothpicks making up six squares. Now re-arrange the 18 matchsticks to make twenty.

New puzzles are published at least twice a month on Fridays. You can check your solution here.

The successor of the sultan (4)

The sultan asked the vizier:
“The tests so far for finding my successor are way too easy. We’ve got to make them harder. There are still dozens of candidates left.”
“This one is definitely more difficult. First, they got to swim”
“So they had in the previous test,” the sultan grumbled.
“If they come up to breath, there heads will be shot off,” the vizier explained. The sultan nodded approval.
“There are four doors.”
“So had the previous test”
“But now there are two labels on every door. So they’ve got to think twice as fast!”

Test 4^***/*****

The first candidate look at the four doors.
“Again only one door hides a treasure,” the vizier explained. “There is a shark behind each of the other three.”
The candidate looked at the labels. He could see that there were two labels on each door, but he couldn’t read them.
“And how many labels are true? Or how many doors have true labels?”
“That is a very good question”, the sultan smiled. “As a matter of fact, knowing which door hides the treasure, it was impossible to decide upon the number of true labels. So how you should decide the number of true labels while you don’t know which door hides the treasure, is beyond me.”

Which door should the candidate open?

New puzzles are published at least once a month on Fridays. Solutions are published after one or more weeks. You are welcome to remark on the difficulty level of the puzzles, discuss alternate solutions, and so on. Puzzles are rated on a scale of 1 to 5 stars. You can check your solution here.