L074 · Allow 10–15 minutes for learners ready to move on. Answers are available after an attempt.
A bag holds 5 red and 4 blue. Find P(two blue without replacement).
4/9×3/8=1/6.
A bag has 4 red and 1 blue. Given the first draw was red, find P(second red without replacement).
After a red, 3 red remain of 4 counters, so 3/4.
Lesson L074: Dependent events and assumptions
Objective: Recognise dependence and the assumptions behind a probability model.
60-minute structure: 0-7 Connect & Check; 7-14 Share; 14-25 Present/model; 25-44 Apply route choice/practice; 44-52 independent exam-style check; 52-60 Recall & Review, WWW/EBI and next step.
I represented the outcomes systematically, used the correct probability rule and checked that the probabilities or frequencies were consistent.
I will show the sample space, branch or set reasoning explicitly, state any dependence or condition and check totals before giving the final probability.
Stretch: A bag holds 5 red and 4 blue. Find P(two blue without replacement).
Deep challenge: A bag has 4 red and 1 blue. Given the first draw was red, find P(second red without replacement).