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

Why Aeroplane windows are round?

Sherlock Holmes was challenged to make a pre-drawn line smaller without erasing it. He did it in fractions of seconds. How?

_ _ _ IE _ _
_ _ _ IE _
_ _ IE _ _
_ _ IE _
_ _ _ _ IE

Like you see, some letters have gone missing from these words that contain the IE pair at some or the other place. The letters that will be used to fill the blanks are given below. Use them and form meaningful words. Can you do that?

A, C, D, F, H, K, L, M, N, N, O, R, R, S, S, S, T, T, Y and Y.

Can you think of a smallest +ve number such that if we shuffle the digits of the number, the new number becomes double the original number?

Complete the series by replacing "?" with the correct number.

ST ND RD TH '?'

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

Suppose we lay down two cups in front of you. One of the cups is filled with tea and the other one with coffee. Now we ask you to take a spoonful of tea and mix it with the coffee. At this moment, the coffee cup has a mixture of tea and coffee. You have to take that mixture (spoonful) and add it back to the tea.

Can you now tell if the cup of coffee has more tea or the cup of tea has more coffee?

Three fair coins are tossed in the air and they land with heads up. Can you calculate the chances that when they are tossed again, two coins will again land with heads up?

There are are five things wrong with this sentence; only geniuses will be able to to spot all of the mitstakes