What occurs twice in a week, once in a year but never in a day?

How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?

Look at the below sequence of letters and tell us what the next letter should be:

O T T F F S S ?

Which three-digit number, made of consecutive digits, like 567, is 2 less than a cube and 2 more than a square?

Replace the question mark with the number below given a simple math problem.

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?

A new Engineering building containing 100 offices had just been completed. John was hired to paint the numbers 1 to 100 on the doors. How many times will John have to paint the number nine (9)?

Mr Red Lives in the red house.
Mr Green Lives in the greenhouse.
Mr Yellow Lives in the yellow house.

Who lives in the Whitehouse?

What is more useful when it is broken?