Transform the word THINK into BRAIN while changing only one letter at a time in a manner that each of the word in the process is a real word!!!

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?

How high do you have to count before you use the letter “a” in the English spelling of the whole number?

What kind of tree can you carry in your hand?

Client Dempsey living in one of the East Coast states of the U.S. was talking to Landon Donovan, who was living in the West Coast state of the U.S.

Dempsey: What time is it?
Donovan: Wow, It is the same time here.

How is this possible?

What is a word made up of 4 letters, yet is also made up of 3. Sometimes is written with 9 letters, and then with 4. Rarely consists of 6, and never is written with 5.

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

How can you tell a raw egg from a hard-boiled egg?

Look at the picture and find out which square is not linked with any of the other squares.

What does does this rebus picture means ?