Count the number of lines in the image below ?

What is harder to catch the faster you run?

Find The Next Number in this series.
1, 2, 6, 42, 1806 ?

In order to complete the racing competition, the Mexico racetrack has to submit its top and the most famous three horses to win the competition. Due to an electrical storm, all the records are cleared and no one knows which horse holds the record. They all look identical and it becomes even more difficult to differentiate the horses. There are 25 horses in the Mexico racetrack. But there can be only five horses at a time on the track. What will the least number of races that can be conducted to find out the three fastest horses?

I am quite hot but become too cold if you remove the first two letters. What am I?

Two in a corner, one in a room, zero in a house, but one in a shelter. What am I?

A Scientist was fifty years old in the year 2000 but he was forty years old in the year 2010. How can this be possible?

PS: It has a logical answer.

An infinite number of mathematicians are standing behind a bar. The first asks the barman for half a pint of beer, the second for a quarter pint, the third an eighth, and so on. How many pints of beer will the barman need to fulfill all mathematicians' wishes?

When it's bad luck to meet a black cat?

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?