How to answer it
- Count all possible outcomes.
- Count the outcomes that fit the question.
- Divide favorable by total and simplify.
Worked example
An original question in the ACT format, already answered.
ACT MathWorked example
A bag holds 5 red, 3 blue and 2 green marbles. One marble is drawn at random.
What is the probability that the marble is not red?
- A1/5
- B3/10
- C1/2
- D7/10
Answer: C. 5 of the 10 marbles are not red (3 blue + 2 green), so 5/10 = 1/2.
The most common trap
Counting only one of the non-red colors. “Not red” includes blue and green.
Practice it
Hourly Prep’s daily sets mix statistics and probability with the rest of ACT Math, and send more of it your way when it’s a weak spot. See how the ACT prep plan works, or browse the other ACT skill guides.