What does the following represent?

N N N N N N N

A A A A A A A

C C C C C C C

There is a shop where written:
Buy 1 for $1
10 for $2
100 for $3
I needed 999 and still only paid $3. How could this be financially viable for the shop-keeper?

What makes this number unique: 8,549,176,320?

A mathematics teacher took exams for his students. Out of the total students, 25% passed both the tests included in the exam. However, only 42% were able to clear the first test.

Can you find out the percentage of those students who passed the first test and also passed the second test?

John and Jacob are twin brothers. One of them is a liar whereas the other one is a truth-teller.

I called their home number and one of them picked up.
I asked. 'Does John lie?' The person replied with a yes.

Whom did I talk with, John or Jacob?

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?

By moving exactly three matchsticks can you make the below equation true.It can be solved by 3 ways.

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

Make a sentence consisting of three words that have the whole alphabet.

A sea diver is a real show-off. He showed everyone that he can hold his breath underwater for 15 minutes.

I went to the diver and told him that I can be underwater for double the time i.e 30 minutes.
He responded that he will give me 100$ if I would be able to do it. I won 100$.

What did I do?