This is from http://www.programaths.com/iqchallenge/index.php It was one of the last items. I know the answer but not the solution and the reasoning to it. Which of the four bottom symbols is the answer, and why?
The answer to this is
D (the last option)
The reason is:
In each pattern the top rows are dependent on the rows below it using a simple rule. The colour of a ball is the colour that occurs the most amongst the three balls nearest to it in the row below. So if you have three consecutive balls in a row, their most used colour is given to the ball directly above the middle one.
The only pattern amongst the four options that satisfies this rule is the last one. The others all have a white ball above a triplet containing two or three black balls.