# Rolling four die

Discrete Mathematics Level pending

Ruby McTube has four six sided die.

They each have the following numbers on their six faces: $$1,1,2,2,4,6$$

If she rolls all four, the probability they each show a different number on top is $$\frac{a}{b}$$ where $$a$$ and $$b$$ are coprime positive integers.

What is $$a+b$$?

Image credit: http://wherethewindsblow.com/

×