Why is 6 afraid of 7?

Two guards were guarding the camp.Guard-1 was looking towards the south to make sure no threat is coming from the road.Guard-2 was looking at the north to make sure no threat is coming from the top. Suddenly Guard-1 ask the Guard-2 why he is smiling?How Guard-1 knows that Guard-2 is smiling?

Why is the Hole below a Lock?

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

Alpha is Beta's sister.

Gamma is a Beta mother.

Delta is Gamma's father.

Tango is Delta's mother.

Then,

How is Alpha related to Delta?

Can you spot the hidden clock in this family photo? Only the most eagle-eyed will find it!

A mules travels the same distance daily.
I noticed that two of his legs travels 10km and the remaining two travels 12km.
Obviously two mules legs cannot be a 2km ahead of the other 2.

The mules is perfectly normal. So how come this be true ?

10+10 and 11+11 can give you the same answer.

Explain how?

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

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