Question

A bag contains nine yellow marbles and nine red marbles. You randomly select two marbles from the bag. What is the probability that both marbles are yellow when you do not replace each marble before selecting the next marble? Write your answer as a decimal rounded to the nearest thousandth.
The probability that both marbles are yellow is about

Answer 1

Answer:   0.235

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Explanation:

9 yellow

9 red

9+9 = 18 total

If you select a marble at random, the chances of it being yellow are 9/18.

If you selected another marble at random, without replacing the first marble, then 8/17 is the probability of getting another yellow marble. I subtracted 1 from the numerator and denominator of 9/18 to go to 8/17.

We multiply the two results

(9/18)*(8/17) = 0.235 approximately

There's roughly a 23.5% chance of getting two yellow in a row, where we don't replace the first marble selected.