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!!!

What is common among 11, 69, and 88?

Move four matchsticks to the below square to form three squares?

I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

After undergoing a successful eye operation, A blind girl has just boarded a train to her home. The doctor asked her to open the bandages after 3 hours. On her train journey, she opened the bandages and within a fraction of the time she commits suicide by jumping off the train.

Though her operation was successful, Why did she commit suicide?

In the following series, a set of numbers is progressing with a particular pattern. Can you deduce that pattern and find the missing set?

(2 + 6), (21 + 6), (58 + 6), (119 + 6), ___

John was running from 40 thieves. John has got 3 gold boxes which weigh as 4kg, 2kg, and 1kg respectively. A witty man asked John to stay with him for seven days in exchange for 1kg gold per day. John needs to stay there for seven days and also do not want to give the witty man any advance. How can John pay for his seven days stay?

Speaking of rivers, a man calls his dog from the opposite side of the river. The dog crosses the river without getting wet, and without using a bridge or boat. How?

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?

What goes up but never comes down?