What always comes into a house through the keyhole?

John is the son of Jacob.
So,
Jacob is the_____of John's father?

There is a jar in which there are two types of candies.
20 blueberries and 16 strawberries. You perform the following steps:
1) You take out two candies.
2) If the two candies are of the same flavour, you add a blueberry one otherwise, you add the strawberry one.

You repeat these two steps till there is just one candy remaining in the jar. Which flavoured candy will be left?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

What am I?

Irene killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

I am dry when I go inside, but wet when I am pulled outside.
The longer I am inside, the stronger I get
When I am completely out, I am wet and I literally sag
Who am I?

There is a wide field of corn. A goose finds its way into the field and starts running. Can you find out till which point the goose can run into the field?

John killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

If,
29 - 1 = 30
9 - 1 = 10
14 - 1 = 15

Based on similar logic, Can you prove that the below algebraic equation is true?
11 - 1 = 10 ?