Why Aeroplane windows are round?

Two friends decide to get together; so they start riding bikes towards each other. They plan to meet halfway. Each is riding at 6 MPH. They live 36 miles apart. One of them has a pet carrier pigeon and it starts flying the instant the friends start traveling. The pigeon flies back and forth at 18 MPH between the 2 friends until the friends meet.

How many miles does the pigeon travel?

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?

Decode the below four famous ciphers:

8P of the SS
1M of the E
1S of the SS
60M in 1H

Can you calculate the probability of getting a sum of six when a dice is thrown twice?

What does below chemistry rebus means?

It has a long neck, A name of a bird, Feeds on cargo of ships, It's not alive,

What is it?

What is at the end of a rainbow?

What kind of tree can you carry in your hand?

What number divided by 4 is the same as that number minus 4?