We have two identical balls in terms of diameter and weight. However, one of them is solid and the other is hollow.

Without knocking the ball, can you find the solid ball?

I’m light as a feather, yet the strongest person can’t hold me for five minutes. What am I?

There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

I have four wings but can't fly.
I express no emotions.
I am found on the exact spot every time you look.
I keep toiling away with a little sound.

Do you know what am I?

These types of puzzles are known as charades. What you have to do is find two words that are referred to in the first stanza and the second stanza and put them together to form the third word in the third stanza.

Just for example, if my first refers to 'off' and my second refers to 'ice', then my whole will be office.

My first is present - future's past -
A time in which your lot is cast.

My second is my first of space
Defining people's present place.

My whole describes a lack of site -
A place without length, breadth, or height.

Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?

Can you write down eight eights so that they add up to one thousand?

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

How many times can you subtract the number two from the number fifty?

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?