How Likely Is It? The Probability Scale from 0 to 1

Student Task

• Draw a long line on the board labeled 0, 1/2 and 1. Read events (the sun will rise tomorrow, it will snow in the classroom) and ask students where they go.
• Do activities 1 and 2 together, counting the outcomes for each question.
• Students complete activities 3 to 6 on their own. Answers are in the answer key.

Classroom Use

• Human probability line: students hold event cards and stand on a rope labeled 0 to 1.
• Counter bags: groups make bags with given probabilities, such as P(red) = 3/4, and swap to check.
• Spinner design: students draw spinners where blue is impossible, likely or an even chance.

Differentiation

Support: give a probability line with the five words already written under 0, 1/4, 1/2, 3/4 and 1. Challenge: students write probabilities as decimals and percentages too, and find the probability that an event does not happen.

Answer Key & Assessment

Activities 1 to 5 check probability words and fractions (answer key included). Activity 6 shows whether students can explain why probabilities are between 0 and 1.

Learning Objectives

• Describe the likelihood of events with words such as impossible, unlikely, even chance, likely and certain.
• Write the probability of an event as a fraction from 0 to 1 when outcomes are equally likely.
• Place events on a probability scale and explain the position.

Teacher Tips

Students often think that because there are two outcomes (win or lose), each has a probability of 1/2. Use a bag with 9 blue counters and 1 red counter to show that the outcomes are not equally likely.

What's Included

• 7-page printable PDF lesson pack: teacher lesson plan with timings, materials and differentiation
• Key vocabulary list (6 words with meanings and examples)
• Student worksheet (6 activities)
• Editable Word version of the worksheet
• Complete answer key (also as a separate PDF)

Additional Files

• Editable Worksheet (DOCX)
• Answer Key (PDF)

Teacher Reviews