A marble is selected at random from a jar containing 30 red​ marbles, 60 yellow​ marbles, and 10 green marbles. Find the theoretical probability that it is either red or green.

Question

​P(red or ​green)=

Answer 1

Number of red marbles = 30
Number of green marbles = 10
Total number of marbles = 30 + 60 + 10 = 100

P(red or green) = P(red) + P(green)
P(red or green) = Number of red marbles/Total number of marbles + Number of green marbles/Total number of marbles
P(red or green) = 30/100 + 10/100
P(red or green) = 40/100
P(red or green) = 0.4

Therefore, the theoretical probability that the marble selected is either red or green is 0.4 or 40%.