Why do we preferably have round manhole covers and not square ones?

You have $100 with you and you have to buy 100 balls with it. 100 is the exact figure and you can't go below or above the numbers and you have to use the entire $100. If there is no kind of tax applied how many of each of the following balls will you be able to buy:

Green Balls costing $6
Yellow Balls costing $3
Black Balls costing $0.10

Now, how many of each must you buy to fulfil the condition given?

Spot what is wrong here in below Picture?

Why is it very easy to weigh a fish?

Sherlock breaks into a crime scene. The victim is the owner who is slumped dead on a chair and have a bullet hole in his head. A gun lies on the floor and a cassette recorder is found on the table. On pressing the play button, Sherlock hears the message 'I have committed sins in my life and now I offer my soul to the great Lord' and followed a gunshot Sherlock smiles and informed the police that's its a murder.

Why did he think so?

If you remove one from eleven, it becomes ten. If you remove one from nine, it becomes ten.

How is this possible?

A seven-year-old kid challenged his classmates that he can make the number one disappear by adding something to it.

How can he do that?

You have three orange, two pink and five purple balls in the drawer beside your bed. There is no electricity and the room is entirely dark. How many balls must you take out to ensure at least one ball of each colour at least?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

I travel all around the world but always stay in the corner. What am I?