What is the word or phrase?

What happened when the wheel was invented?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

Seven Robbers robbed a bank and hide the coins in a lonely place.
They decide to divide the money equally the next morning. Two greedy robbers decided to cheat the others and reach the place at night. They equally divided the coins between them, one coin left. So they called another robber and then they decided to divide equally among the three. Sadly again one coin left. The same thing happened to the 4th 5th and the 6th robber.
However, when the 7th robber reached in the morning, they can divide the coins equally.

How many coins were there in total?

You need to remove two matchsticks to make the below equation true. Can you do it ?

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

The first box has two white balls. The second box has two black balls. The third box has a white and a black ball.

Boxes are labeled but all labels are wrong!

You are allowed to open one box, pick one ball at random, see its colour and put it back into the box, without seeing the colour of the other ball.

How many such operations are necessary to correctly label the boxes?

There is a place where if I stand up straight, I will still be considered sideways.

What is full of holes but still holds water?

What you cannot hold but it is yours?