Railroad Crossing, look out for the cars. Can you spell that, without any R's ?

What does this rebus mean?

O
N
C
E
TIME

Suppose you are sitting in an interview and the interviewee asks you an aptitude question.

You have three buckets with a capacity of 4 litres, 8 litres and 10 litres and you have a large tank of water. Now you have to measure 3 litres of water precisely using those buckets. How will you do it?

What can go up a chimney down, but can’t go down a chimney up?

In the picture given below, can you find out which digit will take place of the question mark?

A girl is twice as old as her brother and half as old as her father. In 50 years, her brother will be half as old as his father. How old is the daughter now?

You can see it everyday, But cannot touch it at will. What is it?

I always drive my customer away.

Who am I?

A newspaper is supposed to have 60 pages, but pages 24 and 41 are missing.
Which other pages won't be there?

What is black when you buy it, red when you use it, and gray when you throw it away?