I am a seven-letter word but if you remove four of my letters I will have one left. What word am I?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

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?

How old is your son? asked a man to his neighbour. My son is five times as old as my daughter and my wife is five times as old as my son. I am twice as old as my wife whereas my grandmother, who is celebrating her eighty-first birthday is as old as all of us put together.

How old is the man's son ?

Things are just as they seem, right? Well, check again.
Can you count the number of tigers in this picture ?

What is the longest word in the dictionary?

If a wheel has 54 spokes, how many spaces are there between the spokes?

What has lots of eyes, but can’t see?

A man has eighty-one cows ( numbered 1,2,3...81 as such). The beauty is that cow no. 1 gives 1ltr of milk, cow no. 2 gives 2ltrs of milk and so on. The man wants to equally distribute the cows among his nine sons so that each one of them gets the same quantity of milk.

Can you start the fire using two pieces of wood?