• Quick retrieval from earlier learning (Follow blood through the heart and lungs). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Following blood from the body to the lungs: where does blood go straight after the pulmonary artery? (right atrium / lungs / right ventricle / vena cava) → lungsPrompt: This side of the heart carries blood low in oxygen.
2. Why is the wall of the left ventricle thicker than the right? (It pumps blood to the lungs only / It is older / It holds more blood / It pumps blood all round the body, so it needs more force) → It pumps blood all round the body, so it needs more forcePrompt: Compare how far blood goes from each ventricle.
3. Following blood from the lungs to the body: where does blood go straight after the left ventricle? (pulmonary vein / aorta / left atrium / lungs) → aortaPrompt: This side of the heart carries oxygenated blood.

• Ask everyone to find their pulse, then jump for 30 seconds and find it again.
• Share the objective: Heart rate, stroke volume and cardiac output. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: A person's stroke volume is 90 cm³ and their heart rate is 72 beats per minute. What is their cardiac output, in cm³ per minute?
• Step 1: 90 × 72 = 6480
• Step 2: So the answer is: 6480 cm³/min
• Answer: 6480 cm³/min
• Pause after each step and ask a student to say what comes next.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. A person's stroke volume is 110 cm³ and their heart rate is 150 beats per minute. What is their cardiac output, in cm³ per minute? → 16500 cm³/minPrompt: cardiac output = stroke volume × heart rate
2. During exercise an athlete's cardiac output is 6 dm³ per minute and their stroke volume is 100 cm³. What is their heart rate, in beats per minute? (1 dm³ = 1000 cm³) → 60 bpmPrompt: Convert the cardiac output to cm³ first.

• 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.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. During exercise an athlete's cardiac output is 15 dm³ per minute and their stroke volume is 100 cm³. What is their heart rate, in beats per minute? (1 dm³ = 1000 cm³) → 150 bpmPrompt: Convert the cardiac output to cm³ first.
2. After exercise, a student counts 22 pulse beats in 30 seconds. What is the heart rate in beats per minute? → 44 bpmPrompt: How many lots of this time fit into 60 seconds?

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-9.