Chance of failure

Question

I play an online based dice game. To hit with a spell you need a 5 or greater roll. I currently roll a 28 sided dice. What is the probability of failing to meet the threshold of 5?

 

Also will you tell me the equation to use in the future, or how I would go about doing this my self?

Answer 1

You just need the percentage of winning rolls divided by all possible rolls.

 

To roll >=5 on a 28 sided dice then the only numbers you would need to avoid are 1-4.  So the odds would just be (28-4)/28 = 24/28 = 6/7.