Why Aeroplane windows are round?

I know a ten-letter word in the English language which can be typed using only the top rows of the computer keyboard.

In a chess board, the queen piece can move horizontally, vertically and diagonally freely. The picture represents the same.Can you place 8 queens on the board in a manner that none of the queens can attack each other?

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

Nine marbles are arranged in the image below. Can you slide two marbles to form a square?

You have two rectangular wires.

Both of them have property that when you light the fire from one end , it will take 60 minutes to get completely burn.

However, they do not burn at consistent speed (i.e it might be possible 1st 20% burn in 50 minutes and 80% can burn in 10 minutes).

So how could you measure 45 minutes ?

Can you count the number of triangles in the given figure?

Find the Next Number in the Sequence

2 9 3 1 8 4 3 6 5 7 ?

Find The Next Number in the series:

12 13 15 17 111 113 117 119 123 ?

What is common among 11, 69, and 88?