Add or Remove Event from Selection

CONCEPTS

Equation

• Probability 1 Event Occurs = Number of desired events / Total number of possible events

Tips

• Adding or removing events must be done in both the numerator AND denominator in a probability equation.

PRACTICE PROBLEMS

Question 1 Given: 2 red balls, 3 green balls, 4 yellow balls. What is probability 2nd ball is red ball? (1st ball is not replaced & is not red)?

-- Answer -- 2/8

2 red balls / (9 total balls - 1 removed ball) = 2/8

ACT PRACTICE PROBLEMS