If we look at the green bar we see that its real height is 2/3 of its shadow. So that means we need to find 2 shadows length for the red bar, the uninterruped part and the one on the wall. Since we now know the formula for the floor shadow - real height is 2/3 of it - meaning the part that makes that shadow is 4 meters long. Then we have to add the part on the wall which is straight up, it has no formula so we just add those 4 meters on the wall to the 4 meters we got from multiplying 2/3 by 6 meters and we have 4 meters + 4 meters = 8 meterss
You are lost in the woods and the path you are following forks into two: a path to the left and one to the right. One path will lead you to safety while the other will cause you to be lost forever.
At the fork are two twin sisters who know which path is which. The sisters are identical in every way except one: one of the sisters always tells the truth while the other always lies.
You can ask only one question and you don’t know which sister is which. What can you say to them so you know which path to take?
Ask one of the sisters which path their sister would tell you to take.
Let’s say the left hand path is the correct one to follow. The sister that lies knows their truthful sister would tell you the left hand path, so as they always lie they will tell you the right hand path.
The honest sister knows their lying sister will tell you the right hand path and because they’re honest, they will tell you this. So you should follow the opposite path to that which you are told, regardless of which sister tells you.
There is a creature which could double its size every day. So, if the creature is put in a tank then it will fill the tank in 10 days.
How many days would it take for the creature to fill a half and how many days to fill a quarter of the tank?
You turn the 7 minute one and the 11 minutes one at the same time. When the 7 one finishes, turn it again. When the 11 one finishes, you know that 4 minutes have passed, with 4 minutes to get to the desired 15, all you need to do now is turn the 7 minute hourglass again since it counted 4 minutes, and when it runs out it'll be exactly 15 minutes.