Thread: the probability of bricks arranged randomly.

if someone have 4 red bricks and 8 blue bricks ,he want to arrange them randomly in circular shape, What is the probability that two red bricks are not side by side?

Hello, Mhmh96!

If someone have 4 red bricks and 8 blue bricks and arranges them randomly in a circle,
what is the probability that two red bricks are not side by side?

There are possible arrangements.
(This includes duplication from rotations.)


Place the 8 blue bricks in a circle, leaving a space between them.

. .


Select 4 of the 8 spaces and insert the red bricks.
There are: ways.


Therefore: .