A bag contains 7 red marbles, 8 blue marbles and 3 green marbles. If two marbles are drawn out of the bag, what is the exact probability that both marbles drawn will be red?
To find the probability of drawing two red marbles, we need to calculate the probability of drawing a red marble on the first draw and then another red marble on the second draw.
The probability of drawing a red marble on the first draw is 7/18 (since there are a total of 18 marbles in the bag and 7 of them are red).
After drawing 1 red marble, there will be 6 red marbles left out of a total of 17 marbles in the bag. So, the probability of drawing a red marble on the second draw is 6/17.
Therefore, the probability of drawing two red marbles is (7/18) * (6/17) = 42/306 = 7/51.
Therefore, the exact probability that both marbles drawn will be red is 7/51.