Good Riddles

Question: Once you are in my sight, you are gone in a flash, and people tend to use me for cash. I am often used as a dire assist, and people often believe that I cause harm, when I am but its catalyst. What am I?

Question: A man wants to start a forest fire.There are 80 trees and you have a lighter. How many trees should he burn?

Question: What key is playful?

Question: Peter is hiding but his head is can seen.

Question: At low tide 14 rungs of a ship are above the water, the rungs are 15 centimeters apart. each 15 mins the water rises 15 centimeters. after 2 hours and 30 mins how many rungs are above the water?