Why is 6 afraid of 7?

Which is faster, Heat or Cold ? Explain.

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

In the city of Brain Teasers, 5% of people do not list their phone numbers. Now if we select random 100 people from the phone directory, then how many people selected will have unlisted phone numbers?

The day before yesterday I was 25 and the next year I will be 28. This is true only one day in a year. What day is my birthday?

A father's child, a mother's child, yet no one's son.

Who am I?

I am a normal creature, but I have five hands. I can even have more but even then I will be considered normal.

Who am I?

There are two arch enemies Messi and Ronaldo who hate each other to an extreme. One day both were going together and a Jeanie appeared in front of them. Jeanie grants 3 wishes to Ronaldo and one to Messi.

Messi replied smartly 'Give me twice whatever Ronaldo demands'.

Ronaldo asked his 1st wish 'Give me 10000 billion dollars. Soon Messi gets 2000 billion dollars.
Ronaldo asked for his 2nd wish 'Give me one mansion in every country in the world. Soon Messi gets two mansions in every country of the world?

What should be Ronaldo's third wish?

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

If an electric train is travelling south, then which way is the smoke going?