Same-Color Probability

What this same-color probability question tests

This is a straightforward probability question that appears frequently in quant interviews to check whether a candidate can correctly handle drawing without replacement. The setup looks simple, but the execution requires careful attention to how probabilities change after the first draw.

To solve problems of this type, you enumerate all the ways the desired outcome can occur (both balls red, both blue, or both green), compute the probability of each case accounting for the reduced population, and sum them. The key is not to confuse "without replacement" with independence—the second draw depends on what was drawn first.

• Conditional probability and the multiplication rule
• Sampling without replacement vs. with replacement
• Exhaustive case enumeration