Below, you will find the mathematical proof that 10 equals 9.99999?. But is that possible or there is something wrong about it? Can you find the error?

x = 9.999999...
10x = 99.999999...
10x - x = 90
9x = 90
x = 10

If a zookeeper had 100 pairs of animals in her zoo, and two pairs of babies are born for each one of the original animals, then (sadly) 23 animals don’t survive, how many animals do you have left in total?

Two girls were born to the same mother, on the same day, at the same time, in the same month and year and yet they're not twins. How can this be ?

When I got four, I have it none.
When I got two, I have it some.
When I got none, I have it all.

What is it?

What has many teeth, but cannot bite?

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

Which is faster, Heat or Cold ? Explain.

How can you throw a ball as hard as you can and have it come back to you even if it doesn't hit anything there is nothing attached to it and no one else catches or throws it.

What has hands, but can’t clap?

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?