Question

What is the probability of not rolling a number larger than 4 with a fair die?

Answer 1

Find the probability of rolling a number bigger than 4 and subtract that by 100%; 

P(5)= 1/6 <-- 6 possible outcomes, 1, 2, 3, 4, 5 or 6
P(6)= 1/6 

You could have rolled a 5 or 6. When the word or is used, the probabilities are added together, when and is used, they are multiplied. 

(1/6)+(1/6)=2/6 

1-P(5)+P(6) 
=1-(2/6) 
=(6/6)-(2/6)
=4/6 

Therefore the probability of not rolling a number larger than 4 is 4/6 or 2/3.

Hope I helped :)