What does this simple rebus mean?

Forwards I am heavy, backward I am not. What am I?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

What does below rebus means ?

It is a nine-letter word.
The exact opposite of the phrase "friendly and outgoing"
It contains the word "over".
It starts will a vowel.

What is it?

What four weights can be used to balance from 1 to 30 pounds?

Three people enter a room and have a green or blue hat placed on their heads. They cannot see their own hat but can see the other hats.
The colour of each hat is purely random. They could all be green, blue, or any combination of green and blue.
They need to guess their own hat colour by writing it on a piece of paper, or they can write 'pass'.
They cannot communicate with each other in any way once the game starts. But they can have a strategy meeting before the game.
If at least one of them guesses correctly they win $10,000 each, but if anyone guesses incorrectly they all get nothing.
What is the best strategy?

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

What is the difference between a jeweller and a jailer?

What does the following BrainBat signifies?

ABCDEFGHIJKLMNOPQRSTUVWYZ

QQQQQQQQQQQQQQQQQQQQQQQQQ.