What is the next number in this matchsticks series riddle?

How high do you have to count before you use the letter “a” in the English spelling of the whole number?

What work can one never finish?

I am an eight letter word and I am a computer terminology.
The second, third and fourth letters make an animal.
The fourth, fifth, sixth, seventh and eighth letters make a weapon.
The first, second, third and fourth letters can be taken as an outcome of any exam.
The fifth, sixth, seventh and eighth letter combine to form a high end typing software.

Can you tell who am I ?

What is so fragile that saying its name breaks it?

2, 3, 5, 9, 17, _ What is the next number in the sequence?

What does this rebus means ?

PROG WORKRESS

A shepherd had 18 sheep, out of which, all but ten died.

Can you tell us how many sheep was he left with?

A large water tank has two inlet pipes (a large one and a small one) and one outlet pipe. It takes 3 hours to fill the tank with the large inlet pipe. On the other hand, it takes 6 hours to fill the tank with the small inlet pipe. The outlet pipe allows the full tank to be emptied in 9 hours.

What fraction of the tank (initially empty) will be filled in 0.64 hours if all three pipes are in operation? Give your answer to two decimal places (e.g., 0.25, 0.5, or 0.75).

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?