If eleven plus two equals one, what does nine plus five equal?

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?

Why do we preferably have round manhole covers and not square ones?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

Rob is taller than Edwin, and Jurgen is shorter than Rob.
Of only one of the following statements, we now certainly know it is correct:

A.Edwin is taller than Jurgen
B.Jurgen is taller than Edwin
C.It cannot be determined if Jurgen or Edwin is the tallest.

The ages of a father and son add up to 66.
The father's age is the son's age reversed.
How old could they be?
(3 possible solutions).

How can you make a TV, a bed, a dog, and a car liquid?

Can you convert the number zero(0) into a positive number using just one mathematical operator ?

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

Can you decipher the two rows to find the hidden word?