Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

I make two people out of one. What am I?

How can one talk without saying a single word?

People put me on the table and cut me but do not eat me. What am I?

You order chicken wings at KFC in the boxes of 6, 9 and 20. What is the largest number of wings that you cannot obtain by buying in any combination of the boxes?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

You can hear me, but you can't touch or see me.

What am I?

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

Arrange the numbers 1, 2, 3, 4, 5, 6, 7, 8 and 9 above and below the division line in a manner that the thus formed fractions equal to 1/3.

(You can use one number only once)

Once upon a time, there was a castle on a square island. The entire island was surrounded by a 14m wide trench. The Romans had wanted to invade the castle and had brought a few wooden planks along with them to facilitate themselves in crossing the moat. The planks were however found to be only 13m long.

The Romans still managed to cross the trench. How did they do it?