What always comes into a house through the keyhole?

Which digit occurred maximum times between the number 1 and 1000?

Can you find the missing number in the third row?
35 20 14
27 12 18
5 2 ?

When I get multiplied by any number, the sum of the figures in the product is always me. What am I?

What is so fragile that saying its name breaks it?

On a certain day, John celebrated his birthday. Two days later, his older twin brother Jacob celebrated his birthday.

Is this even possible? How can it be?

You bought me for dinner but never eat me. What am I?

I inserted a coin in a bottle and closed its mouth with the help of a cork. Now, I was able to take the coin out from the bottle without taking out the cork or breaking the bottle. Can you tell me how I did it?

Take one out and scratch my head, I am now black but once was red. What am I?

A Scientist was fifty years old in the year 2000 but he was forty years old in the year 2010. How can this be possible?

PS: It has a logical answer.