What is the probability of drawing both blue balls in the two draws?

• A. 1/7
• B. 1/21
• C. 2/21
• D. 3/21

Answer: (B)

This question tests drawing without replacement and how to combine probabilities across sequential draws. With two blue balls among seven total, you want both drawn balls to be blue. Think of the draws one by one: the first draw is blue with probability 2/7, and after removing one blue, the second draw is blue with probability 1/6. Multiply these: (2/7) × (1/6) = 2/42 = 1/21. Another way to see it is by counting: there are C(7,2) = 21 possible pairs you could draw, and only one of those pairs is the two blue balls. So the probability is 1/21.