What is black when you buy it, red when you use it, and gray when you throw it away?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

Whats the next number in the below number sequence pattern.

If there are fifteen crows on a fence and the farmer shoots a third of them, how many crows are left?

Why do people go to bed?

In a competitive exam, each correct answer could win you 10 points and each wrong answer could lose you 5 points. You sat in the exam and answered all the 20 questions, which were given in the exam.
When you checked the result, you scored 125 marks on the test.

Can you calculate how many answers given by you were wrong?

Eight of us go fourth, not back, to protect our king from an attack. What are we?

How is the moon similar to a dollar?

I can prove why 1 = 2

* Lets say y = x
* Multiply through by x xy = x2
* Subtract y2 from each side xy - y2 = x2 - y2
* Factor each side y(x-y) = (x+y)(x-y)
* Divide both sides by (x-y) y = x+y
* Divide both sides by y y/y = x/y + y/y
* And so... 1 = x/y + 1
* Since x=y, x/y = 1 1 = 1 + 1
* And so... 1 = 2

How is this possible?

You are given four results as below:
1111 = F
2222 = E
3333 = T
Then, can you find out how to code 4444?