What you cannot hold but it is yours?

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?

You are presented with three boxes. One of them has a red ball inside and the other two have a black ball inside each of them. You are asked to pick up the one with red ball and you pick one. Now, one of the other boxes is opened and it is found to have a black ball.

You are presented with a chance to change your box with the one that is left closed. Will you change your box? Why or why not?

Why is it very easy to weigh a fish?

I got a bee but no honey.
got an eye but am still blind.
got a sea but no water.
got a tea but no coffee.
got a why but no answer.

What Am I?

Can you calculate the probability of getting a sum of six when a dice is thrown twice?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

If,

20 % 5 = 24

21 % 7 = 33

42 % 6 = 67

Then;

66 % 6 = ?

As easy as you can get into me, it is as hard to get out of me.

Do you know what I am?

Which is faster, Heat or Cold ? Explain.