Why do we preferably have round manhole covers and not square ones?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

Can you name some countries which do not have the alphabet 'A' in them?

One night, a woman receives a call from the police. They tell her that her husband was murdered and that she should come to the crime scene as soon as possible. The woman drops the phone, shocked, and drives 20 minutes to the crime scene. As soon as she reaches the crime scene, the police arrest her and she is convicted of murder. How do the police know she committed the crime?

Below, you can see some coding:
January = 1017
February = 628
March = 1335
April = 145
May = 1353
June = 1064
July = 1074
August = 186

Now deciphering the way it has been coded, can you find out how September will be coded?

Can you tell a 3D object that has just two surfaces?

Which statement is true out of the following?
One statement here is false.
Two statements here are false.
Three statements here are false.

Look at the picture and find out which square is not linked with any of the other squares.

Can you find the mistake in the below statement?

There are six people in a family namely M, N, O, P, Q and R.

R and O are brother and sister.

N is the brother of Q's husband.
P is the father of M and grandfather of R.

How many male members are in the family?