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

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

A famous swimmer can swim downstream in a lake in exactly 40 minutes with the lake current.
He can swim upstream in that lake in exactly 60 minutes against the lake current.
The length of the lake is 2 km.

How long he can cover the distance of one side at a still lake with no current?

Can you replace the question mark with the correct number?

It has a long neck, A name of a bird, Feeds on cargo of ships, It's not alive,

What is it?

Why do you find that most of the buildings are deprived of the 13th floor?

In the following series, a set of numbers is progressing with a particular pattern. Can you deduce that pattern and find the missing set?

(2 + 6), (21 + 6), (58 + 6), (119 + 6), ___

What is the word or phrase below?
R | E | A | D

You board a train. The train will have to enter a tunnel soon. You are claustrophobic. Which place is the best for you to sit?

My grandson is about as many days as my son in weeks, and my grandson is as many months as I am in years. My grandson, my son and I together are 120 years. Can you tell me my age in years ?