The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

A tree doubled in height each year until it reached its maximum height over the course of ten years. How many years did it take for the tree to reach half its maximum height?

If you say my name, I will no longer exist. What am I?

I have a big mouth and I am also quite loud! I am NOT a gossip but I do get involved with everyone's dirty business.

I have 50 feet long of cloth, I need to create 50 handkerchiefs each size of 1 foot. I take one minute to cut a 1-foot handkerchief. So how long will it take to cut 50 handkerchiefs?

My grandson is about as many days as my son in weeks, and my grandson is as many months as I am in years. My grandson, my son and I together are 120 years. Can you tell me my age in years ?

You see a mathematical expression in the picture. Can you think of a movie that this expression refers to?

Can you make four (4) nines (9) equal 100?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

I am white when I am dirty, and black when I am clean. What am I?