What is the centre of gravity?

What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9?

Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

what does this picture(rebus) riddle means ?

Assume the given figure to be a delicious doughnut. Yes, now you can concentrate more on the puzzle. So you have this delicious doughnut in your refrigerator when your friends come knocking at the door. There are eight of them. Now you have to make three cuts in this doughnut so that each one of you nine people can enjoy a piece of it. Neither you nor your friends would mind the size of their piece as long as they are getting it. How will you do it?

Decode the below four famous ciphers:

8P of the SS
1M of the E
1S of the SS
60M in 1H

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

Thirty friends were on a hiking trip when they decided to enjoy the bonfire. They assembled for it and agreed to play a game. For that, they divided themselves into five teams with seven members each, forming five rows.

How did they manage to achieve this formation?

The Federal bank of London is abducted by the robbers. The head of the robbers asked the cashier to empty their money vault to them and when suddenly cashier got a call from her father. To avoid any suspicion, the robber asked the cashier to pick the call and reply her father in the shortest manner possible.

The cashier told her father "Is there an emergency father, Call me when you are free and I will help you in your furnishing" and then the cashier hung up the phone.

After 10 minutes, police arrived at the crime scene.

How did the police know about the robbery?