how do you know when to add or multiply for probablity ex a bag is filled with 3 red 4 blue 3 yellow marbels what is the pro that you will draw two times and both will be red ( you replace)

Question

anonymous · Answer

help

anonymous · Answer

you put the first marble back in the bag after drawing it?

anonymous · Answer

yes

anonymous · Answer

in general you multiply if 
a) the events are independent and 
b) you have an AND statement, as in what is the probabilty the first  one is red AND the second one is red

anonymous · Answer

you often add when you have an OR  statement, if the events are mutually exclusive, like "what is the probability you roll a 7 or an 8

anonymous · Answer

ok

anonymous · Answer

in your example above you would multiply the two probabilities together

anonymous · Answer

ahh ok i understand thnks for helping:)