What goes up but never comes down?

Two-person want to cross a river. Only one boat is present on the riverside that can carry only one person at a time.

However, they still manage to cross the river. How is it possible?

using four eights (8) and a one (1) and one mathematical symbol , create the number 100

In the figure that has been attached to this question, each digit represents a digit. The similar letters carry the same integer value. Can you expose the original digits?

You throw me out when you want to use me and you take me in when you don't want to use me.

Who Am I?

Can you think of a smallest +ve number such that if we shuffle the digits of the number, the new number becomes double the original number?

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

What is it?

A network of 20 x 10 squares is given to you.

Can you calculate how many unique squares and rectangles can be formed combining two or more individual squares ?

In a school, there are four subjects. Seventy percent of students study English, seventy five percent of students study Science, eighty five percent of students study Mathematics and eighty percent of students study Spanish.

Can you calculate the percentage of students that study all four subjects?

John was so frustrated to be the suspect of being a sleeper terrorist that he shoot himself right between the eyes with a revolver in his toilet. The revolver and the bullets were accurate. Minutes later John walks out of the toilet unharmed.
How can this be possible?