What is always in front of you but can’t be seen?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

What runs around the whole yard without moving?

What is the four-digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?

Today, I celebrated my 32nd birthday but I was born in 1972.
How is this possible?

Three men in a cafe order a meal the total cost of which is $15. They each contribute $5. The waiter takes the money to the chef who recognises the three as friends and asks the waiter to return $5 to the men.

The waiter is not only poor at mathematics but dishonest and instead of going to the trouble of splitting the $5 between the three he simply gives them $1 each and pockets the remaining $2 for himself.

Now, each of the men effectively paid $4, the total paid is therefore $12. Add the $2 in the waiters pocket and this comes to $14. Where has the other $1 gone from the original $15?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

We have four gears with below features=> Both Gear A and D has 60 teeth=> Gear B has 40 teeth=> Gear C has 20 teeth=> Every two minutes, Gear B makes 25 full turns.What is the relative speed of Gear A and Gear B?

Why did the Girl throw the butter out of the window?