Math lesson plan · 10th grade (Year 11 in England) · 60 minutes
Use the addition rule P(A or B)
Statistics and probability
CCSS HSS.CP.B.7England: GCSE Higher Probability
Objective and success criteria
Students will: Use the addition rule P(A or B).
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Complete and use a two-set Venn diagram
Leads to: the next skill in this area.
Materials: Squared paper for charts, Class survey data, Sticky notes for a live chart, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 6 min
- Quick retrieval from earlier learning (Complete and use a two-set Venn diagram). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- In a club of 38 students, 24 play chess, 14 play the guitar and 9 do neither. How many do both? → 9Prompt: How many do at least one activity?
- Venn diagram of 30 people: apples only 3, bananas only 11, both 6, neither 10. A person is chosen at random. Find the probability they like apples or bananas (or both). Give a fraction in its simplest form. → 2/3Prompt: Decide which regions of the diagram you need.
- In a club of 24 students, 9 play chess, 15 play the guitar and 6 do neither. How many do both? → 6Prompt: How many do at least one activity?
Hook · 6 min
- Take a quick class survey (favorite fruit, travel to school) and ask what the results tell us.
- Share the objective: Use the addition rule P(A or B). Read the success criteria together.
I do: model it · 12 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: P(A) = 0.5, P(B) = 0.5 and P(A and B) = 0.2. Find P(A or B).
- Step 1: 0.5 + 0.5 − 0.2 = 0.8
- Answer: 0.8
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 12 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- P(A) = 0.3, P(B) = 0.3 and P(A and B) = 0.2. Find P(A or B). → 0.4Prompt: P(A or B) = P(A) + P(B) − P(A and B).
- A card is drawn from a standard 52-card deck. Find the probability that it is a number card from 2 to 10 or a diamond. Give a fraction in simplest form. → 10/13Prompt: Count each group, then subtract the cards counted twice.
You do: independent practice · 17 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 7 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- P(A) = 0.6, P(B) = 0.2 and P(A and B) = 0.1. Find P(A or B). → 0.7Prompt: P(A or B) = P(A) + P(B) − P(A and B).
- A card is drawn from a standard 52-card deck. Find the probability that it is a number card from 2 to 10 or a diamond. Give a fraction in simplest form. → 10/13Prompt: Count each group, then subtract the cards counted twice.
Watch out for
- Forgetting to put data in order before finding the median.
- Reading a bar's height wrongly when the scale goes up in 2s or 5s.
Support and stretch
Support
- Review first: Complete and use a two-set Venn diagram.
- Use concrete materials: squared paper for charts.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/math/grade-10.
Free lesson plan from eurekami.com/lesson-plan-builder