Two guards were on duty outside a barracks. One faced up the road to watch for anyone approaching from the North. The other looked down the road to see if anyone approached from the South. Suddenly one of them said to the other, "Why are you smiling?"

How did he know his companion was smiling?

Give it food and it will live; give it water and it will die.

Which is faster, Heat or Cold ? Explain.

My location can be determined by the below rebus.
So where am i ?

What can run but never walks, has a mouth but never talks, has a head but never weeps, has a bed but never sleeps?

My thunder comes before the lightning; my lightning comes before clouds; my rain dries all the land it touches. What am I?

If you toss a coin 10 times and it lands heads up every time, what are the chances it will land heads up if you toss it again?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

Why is it very easy to weigh a fish?

Outside a tattoo artist's shop, there was a signboard which read 'I make tattoos on only them who do not tattoo themselves'.

Reading it what do you think, does the tattoo artist tattoo himself?