Replace the question mark with the correct number below.

I make a loud sound when I’m changing. When I do change, I get bigger but weigh less. What am I?

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?

There is a square of a particular number which when doubled, becomes 7 more than its quarter.

Can you find the number?

Can you make the number 24 by utilizing the numbers 1, 3, 4 and 6? You must use one number only one time and you can use mathematical operation symbols anytime anywhere.

A father's child, a mother's child, yet no one's son.

Who am I?

What four weights can be used to balance from 1 to 30 pounds?

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.

In the image below, you can see two glasses and two matchsticks.You need to move four matchsticks in such a manner that the crosses come inside the glasses. Note: you cannot move the crossed.

Find the number of squares in the below-given picture.