Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

Teacher ask the student

'Why are you standing on that chair in music class ?'.

what did student replied ?

Here is a Swiss Cross. You have to make two straight cuts in the figure so that it is divided into four congruent pieces. Also, you should be able to join these pieces into a square then. Can you accept this challenge?

There are three Athletes (John, Tarun and Harish) and their individual Coaches (Jacob, Meenaxi and Priyanka) standing on the shore.
No Coach trusts their Athlete to be near any other Coach unless they are also with them.
There is a boat that can hold a maximum of two persons.
How can the six people get across the river?

You see a mathematical expression in the picture. Can you think of a movie that this expression refers to?

I’m tall when I’m young, and I’m short when I’m old. What am I?

A father's child, a mother's child, yet no one's son.

Who am I?

If a zookeeper had 100 pairs of animals in her zoo, and two pairs of babies are born for each one of the original animals, then (sadly) 23 animals don’t survive, how many animals do you have left in total?

A boy was locked in a room by some robbers. All that is in the room is a piano, a calendar, and a bed. The room is locked from the outside. What does he eat, drink, and how does he escape and get out?