What is the word or phrase?

A man has eighty-one cows ( numbered 1,2,3...81 as such). The beauty is that cow no. 1 gives 1ltr of milk, cow no. 2 gives 2ltrs of milk and so on. The man wants to equally distribute the cows among his nine sons so that each one of them gets the same quantity of milk.

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

A woman named Maria was at the funeral of her mother. She met a nice young man that she had never seen before and after the service, they spent a bit of time together. Then she got busy and didn’t get his name or phone number before he left. She tried to find him, but no one knew who he was or how to contact him. A few weeks later, Maria’s older sister dies and the police suspect murder. Who killed the sister?

There’s a one-story house in which everything is yellow. Yellow walls, yellow doors, yellow furniture. What colour are the stairs?

If a boy blows 18 bubbles,
Then pops 6 eats 7 and then
He pops 5 and blows 1.
How many are left?

A woman lives in a Tall building thirty-six floors high and served by several elevators which stop at each floor going up and down. Each morning she leaves her apartment and goes to one of the elevators. Whichever one she takes is three times more likely to be going up than down. Why?

Can you identify if it's a murder or a suicide ?

Which English verb becomes past tense just by rearranging the letters?

What goes through cities and fields, but never moves?