What is the fastest way to double your money?

A maths symbol is hidden in the below Bar Graph. Can you decipher it?

Can you make four (4) nines (9) equal 100?

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

I guess 76.8% of readers will like this riddle.

What's the least number of people should read this post?

Find the Odd One Out?
84129
32418
47632
36119
67626
72927

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

There are five people. One of them shot and killed one of the other five.
We know following clues:
1. Dan ran in the NY City Marathon yesterday with one of the innocent men.
2. Mike consider being a farmer before he moved to the city.
3. Jeff is a top notch computer consultant and wants to install Ben new computer next week.
4. The murderer had his leg amputated last month.
5. Ben met Jack for the first time six months ago.
6. Jack has been in seclusion since the crime.
7. Dan used to drink heavily.
8. Ben and Jeff built their last computers together.
9. The murderer is Jack's brother. They grew up together in Seattle.

Consider yourself to be a famous detective "Sherlock Homles", Can you find the killer?

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.

When 99 is considered higher than 100?