What is common among 11, 69, and 88?

A Detective reviewed the information they had on the case so far.

A lady named 'Caterina' was found shot and they already had a list of suspects - Ankit, Tarun, Harish, Manoj and Manish.
The killer is a fan of challenges him by leaving notes ad various places.
* The first was found in a toilet room.
* The second was found in an art room.
* The third was in a restroom.
* the fourth in an underwater room.
* The fifth at the no-smoking room.

All of the notes read the same thing, 'The clues are where you find the notes.' Yet, nothing was found at any place the notes were.
Detective the genius, immediately solved the case.
Who was the killer?

Can you calculate the probability of getting a sum of six when a dice is thrown twice?

Find the number of squares in the below picture

By moving exactly three matchsticks can you make the below equation true.It can be solved by 3 ways.

Which city is three-fifths chick two third cat and 50% goat?

Find the next number in the sequence

1, 2, 6, 21, 88, __?

A seven-year-old kid challenged his classmates that he can make the number one disappear by adding something to it.

How can he do that?

What brings you down but never up?

What always comes into a house through the keyhole?