What occurs twice in a week, once in a year but never in a day?

What is the next number in this matchsticks series riddle?

Can you find out the remainder when 3^300 is divided by 5?

John asked Jack, "The time right now is 7 pm. Can you tell me what will be the time 23, 999, 995 hours later ?"

While Bella does not know the answer, do you ?

What word begins and ends with an E, but has only one letter?

A man hijacks an aeroplane transporting both passengers(8 of them) and valuable cargo. After taking the cargo, the man demands nine parachutes, puts one of them on, and jumps, leaving the other eight behind. Why did he want eight?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.

Today, I celebrated my 32nd birthday but I was born in 1972.
How is this possible?

What question can you never answer yes to?

How many triangles are there in the picture below?