Mary has a bag that contains 5 green marbles, 7 red marbles and 9 blue marbles. Witout looking, Mary draws a marble from the bag. What is the probability that Mary will draw a red or a green marble?

Question

anonymous · Answer

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anonymous · Answer

there are 5+7+9 = 21 marbles in the bag

picking one time, the chance to get a red or green marble is just as high as the share of those marbles in the bag. green and red are 5+7 = 12 marbles, so the chance to get any of those is 12 / 21