What has a ring but no finger?

What word is represented by this rebus?

What building has the most stories?

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

A rubber ball keeps on bouncing back to 2/3 of the height from which it is dropped. Can you calculate the fraction of its original height that the ball will bounce after it is dropped and it has bounced four times without any hindrance ?

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.

In the image below, you can see two glasses and two matchsticks.You need to move four matchsticks in such a manner that the crosses come inside the glasses. Note: you cannot move the crossed.

Identify the 10 differences between the two given pictures.

What question can you never answer yes to?

Take away my first letter, then take away my second letter. Then take away the rest of my letters, yet I remain the same. What am I?