It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

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.

I am a normal creature, but I have five hands. I can even have more but even then I will be considered normal.

Who am I?

How can you drop a raw egg from a height onto a concrete floor without cracking it?

In the city of Brain Teasers, 5% of people do not list their phone numbers. Now if we select random 100 people from the phone directory, then how many people selected will have unlisted phone numbers?

Can you count the number of triangles in the given figure?

There are six people in a family namely M, N, O, P, Q and R.

R and O are brother and sister.

N is the brother of Q's husband.
P is the father of M and grandfather of R.

How many male members are in the family?

What number do you get when you multiply all of the numbers on a telephone's number pad?

There are nine dots in the picture that has been attached with this question. Can you join all the dots by drawing four straight lines without picking up your pen?

In the given figure, move three matchsticks so that the resulting figure contains two rectangles.