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?

No matter how little or how much you use me, you change me every month. What am I?

Look at the picture and find out which square is not linked with any of the other squares.

When I asked a girl's name she told me her name is the date '07/09/2001'.

I thought for a few seconds and then I got her name. Do you?

Place a mathematical symbol between the numerals 5 and 9 in such a way that the resulting number is greater than 5 but smaller than 9.

Buy me, smell me or deliver me, I do not change.

Who am I?

Can you solve this picture maths equation?

Can you spot what's wrong with the following sentence?

PETER WAS ANGRY AT
HIMSELF BECAUSE HE
ACCIDENTALLY LEFT THE
THE KEYS TO HIS CAR
AT HIS FRIEND'S HOUSE.

Before the start of the car race, John and Jacob have the same amount of fuel in their car. With this fuel, John can drive for 4 hours while Jacob can drive five hours.
After a time they realize that the amount of fuel left in John's car is 1/4th of the fuel in Jacob's.

For how long they are racing?

When is the top of a mountain similar to a savings account?