Probability is expressed as
number of favorable outcomes/number of total outcomes
But probability can also be classified as theoretical probability and experimental probability. The theoretical probability is the normal probability of each outcome while the expreimental probability is the probability of an outcome given that trials have been made.
In this scenario,
total number of trials = 400 + 195 + 405 = 1000
favorable outcomes = number of times that we landed on yellow = 405
the experimental probability of landing on yellow is
405/1000 = 0.405
