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

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

All of Jacob's shoes are red except two.
All of Jacob's shoes are green except two.
All of Jacob's shoes are yellow except two.

How many shoes does Jacob have?

There are 2 sand hourglasses.

The small one can measure 5 hours and the large one can measure 7 hours.

How can we measure 16 hours with 2 sand hourglasses running together ?

Name one eight-letter word with 'kst' in the middle, 'in' the beginning, 'and' at the end.?

Complete the series by replacing "?" with the correct number.

ST ND RD TH '?'

If you were to put a coin into an empty bottle and then insert a cork into the neck, how could you remove the coin without taking out the cork or breaking the bottle?

In a university, a professor gave a set of three problems to the three brilliant students of his class. See the image for the questions.

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?

Can you solve the maths in the below-given picture equation?