What goes up but never comes down?

What do you see in the image below

A thief enters a store and threatens the clerk, forcing her to open the safe. The clerk says, “The code for the safe is different every day, and if you hurt me you’ll never get the code.” But the thief manages to guess the code on his own. How did he do it?

Move four matchsticks to the below square to form three squares?

I know a 5-digit number having a property that With a 1 after it, it is three times as large as it would be with a one before it.

Guess the number?

In the given figure, you can see that four match sticks are used to form a square. Can you form five squares by using six matches?

Can you replace the question mark with the correct number in the below table sequence?

Using the clues below, what four numbers am I thinking of?

The sum of all the numbers is 31.
One number is odd.
The highest number minus the lowest number is 7.
If you subtract the middle two numbers, it equals two.
There are no duplicate numbers.

Our product and our sum always give the same answer. Who are we?

81 x 9 = 801. What must you do to make the this equation true?