ACT · Pre-Algebra · Elementary probability
Question act-q-00270
Medium Multiple choice Calculator OK
The question
A bag contains 7 red marbles and 7 blue marbles. If one marble is drawn at random, what is the probability that it is red?
- 7/14
- 7/7
- 7/7
- 7/14
Show answer & worked solution
Answer: 7/14
Worked solution. Probability = favorable outcomes / total outcomes = 7 / 14.
Why each wrong choice is wrong. Common distractors compute the probability of the other color, or use the wrong color count in the numerator or denominator.
Test-day tactic. Probability is favorable over total. Total includes everything in the sample space, not just the unfavorable outcomes.
About this question type
Items ask for the probability of a single event, of compound independent events, or for "at least one" using the complement rule.
You will see a question shaped like this one on roughly every other official ACT form, typically at a moderate position in the section — solidly within the range that separates a 600-band student from a 700-band student. Treat any miss in this subtopic as a signal to drill the subtopic page before you do another full practice test.