What month of the year has 28 days?

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

A boy and a girl are sitting on the porch.
"I'm a boy," says the child with black hair.
"I'm a girl," says the child with red hair.
If at least one of them is lying, who is which?

If,

A + B = C
D - C = A
E - B = C

Based on the above equations, find out the answer for:

D + F = ?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

He loves to dance, twist and prance, he shakes his tail, and as a way he sails, wingless he flies into the sky. What is he?

Below the four parts have been reorganised. The four partitions are exactly the same in both arrangements. Why is there a hole?

I’m tall when I’m young, and I’m short when I’m old. What am I?

Below, you will find the mathematical proof that 10 equals 9.99999?. But is that possible or there is something wrong about it? Can you find the error?

x = 9.999999...
10x = 99.999999...
10x - x = 90
9x = 90
x = 10

You board a train. The train will have to enter a tunnel soon. You are claustrophobic. Which place is the best for you to sit?