Can anyone tell me a word in the English dictionary which has a silent 'z'?

It is always ahead of me yet I can never see it. What is it?

Replace the question mark with the number below given a simple math problem.

How can you tell a raw egg from a hard-boiled egg?

Can you find the odd number in the following five choices?

1) 482636
2) 259807
3) 865195
4) 104739
5) 391744

What do you answer even though it never asks you questions?

We have shown you a regular water barrel as below. Without using any measuring device can you check if the barrel is more than half-filled or less than half-filled?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

You measure my life in hours
I serve you by expiring
I vanish faster when I am thin
and slower when I am thick
The wind is my energy
What am I?

Three ants are sitting at the three corners of an equilateral triangle. Each ant starts randomly picks a direction and starts to move along the edge of the triangle. What is the probability that none of the ants collide?