Duration and Conversions

Overview

Lesson 6 of 7 in Measuring Tools and Units for a class of 20 Year 6–8 students. Students measure short durations, read analogue and digital times, calculate elapsed time, and apply common conversion relationships across time, length, mass and capacity.

Learning intentions

• WALT measure duration and convert between common units of measure.
• WALT read and represent time using analogue and digital clocks.
• WALT use known relationships to solve measurement problems.
• WALT explain whether a measurement answer is reasonable.

Success criteria

• I can select an appropriate unit for duration.
• I can calculate elapsed time from a start and finish time.
• I can use relationships such as 1 minute = 60 seconds and 1 metre = 100 centimetres.
• I can explain whether my answer is reasonable.

Curriculum links

• Measurement: estimate, measure and compare duration using seconds, minutes, hours and days.
• Measurement: convert between commonly used metric units for length, mass and capacity.
• Number and algebra: use multiplication and division facts to solve practical conversion problems.
• Key competencies: thinking; managing self; participating and contributing; using language, symbols and texts.

Lesson structure (30 minutes)

1. 0–4 minutes – Hook and prior knowledge

Open with the hook and learning intentions. Show an analogue clock and its matching digital time, then ask: “Which unit would you use to measure brushing your teeth, a school day and a long weekend?” Students discuss with a partner and justify their choices.

Briefly revisit the WALT and success criteria. Reinforce the language seconds, minutes, hours, days, elapsed time, start time and finish time orally and visually.

2. 4–9 minutes – Model time and elapsed time

Use the time modelling slides and a concrete classroom clock or the interactive clock. Model reading an analogue time, matching it to a digital display, and finding elapsed time by counting forwards.

Example: “A game starts at 9:40 am and finishes at 10:15 am. How long did it last?” Think aloud: 20 minutes to 10:00, then 15 minutes, so the total is 35 minutes. Show that crossing an hour may require two jumps.

3. 9–14 minutes – Quick timing investigation

In mixed-ability pairs, students choose one safe, short classroom action, such as writing their name, stacking five books or doing five star jumps. One student performs while the other uses a stopwatch; then they swap roles.

Display the instructions using the timing investigation instructions. Students record the duration in seconds and discuss whether seconds or minutes is the more appropriate unit. Complete one example together, including checking that the result is sensible.

4. 14–19 minutes – Conversion families

Display the conversion teaching slides. Teach one family at a time, using repeated oral language and a clear colour-coded structure:

• 1 minute = 60 seconds; 1 hour = 60 minutes; 1 day = 24 hours.
• 1 metre = 100 centimetres.
• 1 kilogram = 1,000 grams.
• 1 litre = 1,000 millilitres.

Use the Units Conversion Ladder as a reference display or hand one copy to each pair. Model both directions, for example, 3 kg = 3,000 g and 2,000 mL = 2 L. Emphasise that converting to a smaller unit usually gives a larger number.

5. 19–26 minutes – Paired practice

Distribute the duration and conversions practice sheet. Students work in pairs, explaining each answer before recording it. Include questions on:

• selecting an appropriate unit;
• reading analogue and digital times;
• calculating elapsed time;
• converting between time units;
• converting metres/centimetres, kilograms/grams and litres/millilitres;
• explaining whether an answer is reasonable.

Pause after three minutes for a brief check using the guided practice and answer-check slides. Invite students to explain strategies rather than only state answers. Calculators may be used after the relationships have been modelled.

6. 26–30 minutes – Plenary and assessment

Return to the plenary slides. Ask students to solve: “A 750 mL bottle is filled four times. How much water is that in litres?” and “A lesson begins at 1:25 pm and ends at 2:10 pm. How long is it?”

Students hold up or state answers, including units, then explain one reasonableness check. Collect the worksheet and note which students can independently select units, calculate elapsed time and convert accurately.

Resources

• the complete lesson slide deck
• the duration and conversions practice sheet
• the Units Conversion Ladder
• Demonstration analogue clock or concrete teaching clocks
• Classroom timer or stopwatch
• Several devices for timing, if available
• Whiteboard and coloured pens
• Pencils and rulers
• Optional calculators for students who need them after modelling

Assessment

• Observe pair discussions and timing activity: listen for appropriate unit selection and correct use of measurement vocabulary.
• Check worksheet responses for accurate conversions, elapsed-time strategies, units and reasonableness explanations.
• Use the two plenary problems as an immediate formative check; record students needing further support in the final unit lesson.

Differentiation

• Provide concrete clocks, a visible number line for elapsed time and colour-coded conversion ladders. Teach one conversion family at a time and model each direction explicitly.
• Use mixed-ability pairs, reduced-choice questions and partially completed examples for students requiring support. Allow calculators after students have identified the conversion relationship.
• For dyslexia-friendly access, use a clear sans-serif font, short instructions, generous spacing, repeated oral language and colour coding. Read questions aloud and allow extra processing time.
• Support EAL learners with illustrated unit symbols, sentence frames such as “I chose ___ because ___” and partner rehearsal before writing. Challenge confident students to explain multiple strategies and check answers using an inverse conversion.