I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

I am under you when I am whole.
I shift above you if you remove the first letter.
I come all around you if you remove the second as well.

Can you tell me who I am?

Which tank will fill first?

There were two grandmothers and their two granddaughters.
There were two husbands and their two wives.
There were two fathers and their two daughters.
There were two mothers and their two sons.
There were two maidens and their two mothers.
There were two sisters and their two brothers.
Yet there are only six, who are buried here,
All are born legitimate and relationships clear.
How can this happen?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

When Jack was six years old he hammered a nail into his favourite tree to mark his height. Ten years later at age sixteen, Jack returned to see how much higher the nail was. If the tree grew by five centimetres each year, how much higher would the nail be?

In the figure, you can see nine stars. What you have to do is connect all of them by using just four line and without lifting your hand i.e. in a continuous flow.

What does the below rebus riddle means?

Find the Next Number in the Sequence

2 9 3 1 8 4 3 6 5 7 ?