You can see it everyday, But cannot touch it at will. What is it?

Find the mistake in the below maths equations

A = 2
A(A-1) = 2(A-1)
A2-A = 2A-2
A2-2A = A-2
A(A-2) = A-2
A = 1

Below rebus represent famous DiCaprio movie. Can you name it?

A man fell off a smuggling boat into deep water. He could not swim and he was not wearing anything to keep him afloat. It took 30 minutes for the people on the boat to realize someone was missing. The missing man was rescued two hours later on the return trip. Why didn't he drown? Note:- He didn't know swimming, the sea was deep, and He wasn't holding anything

Can you make four (4) nines (9) equal 100?

What has one letter and starts with an E?

What is the centre of gravity?

A pond had 60 fish, out of which, all but 20 died.
How many fishes are now present in that pond?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

There is a bag which have 21 blue balls and 23 red balls. You also have 22 red balls outside the bag. Randomly remove two balls from the bag. * If they are of different colors, put the blue one back in the bag. * If they are the same colour, take them out and put a red ball back in the bag. Repeat this until only one ball remains in the bag. What is the color of the sole ball left in the bag ?