Finding Start Times

Overview

Students solve the problem “What time did they start their run?” by reading analogue and digital clocks, using minutes as the unit of measure, and working backwards along a timeline. The lesson builds on familiar time-reading and introduces calculating a start time from an end time and duration.

Learning intentions

• WALT read and record times in minutes using analogue and digital clocks.
• WALT use a timeline to calculate a start time.
• WALT explain how hours and minutes are connected within 24 hours.
• WALT use accurate mathematical language when discussing time.

Success criteria

• I can read an analogue and digital clock to the nearest minute.
• I can show a time on a timeline using hours and minutes.
• I can calculate when an event started when I know the finish time and duration.
• I can explain my strategy using words, numbers or a diagram.

Curriculum links

• Measurement — measure duration using appropriate time-based units.
• Measurement — use minutes and hours to estimate, measure and compare duration.
• Mathsteasers — solve higher-order thinking questions and deepen understanding.
• Mathematical communication — explain strategies, justify answers and respond to others’ ideas.

Lesson structure (30 minutes)

1. 0–4 min · Hook and estimate. Display the opening question in the hook and time image: “A run finished at 10:20 and lasted 35 minutes. What time did it start?” Students make a quiet estimate, then share what information they would need to solve it.

2. 4–9 min · Revisit time language. Use the vocabulary and clock slides to review hours, minutes, digital, analogue and 24 hours. Teacher models that 60 minutes make one hour and demonstrates moving backwards from 10:20 by 20 minutes to 10:00, then by 15 minutes to 9:45; students show the movements with finger timelines or mini whiteboards.

3. 9–14 min · Guided modelling. Open the relevant example on the worked timeline example and model the question, “What time did they start their run?” Draw a timeline from the start to the finish, partition the duration into useful jumps, and calculate 10:20 − 35 minutes = 9:45. Students solve a similar example with the teacher: a run finishes at 2:10 and lasts 25 minutes.

4. 14–23 min · Textbook and workbook practice. Direct students to Textbook pages 104–107, focusing on the Explore question and examples about finding a starting time. Then students complete selected questions on Workbook pages 71–72 independently or with a partner, using the start-time practice worksheet for additional recording space and a timeline scaffold. Teacher works with a small group, checking that students cross an hour boundary accurately.

5. 23–27 min · Compare strategies. Display the discussion prompts and invite two or three students to explain different methods, such as counting backwards in jumps, subtracting minutes, or using a number line. Students compare methods with a partner and identify which strategy is easiest for them and why.

6. 27–30 min · Exit check and reflect. Give the class the exit question from the final check: “The race finished at 11:05 and lasted 40 minutes. What time did it start? Show your thinking.” Students complete it independently and circle whether they feel confident, nearly confident or need more practice.

Resources

• Teacher display or whiteboard
• the complete time lesson deck
• Textbook, pages 104–107
• Workbook, pages 71–72
• the start-time practice worksheet
• Mini whiteboards, pens and cloths
• Demonstration analogue clock with movable hands
• Pencils and rulers for drawing timelines

Assessment

• Listen for accurate use of hours, minutes, analogue, digital and 24 hours during discussion.
• Check students’ timelines and calculations during workbook practice, particularly when the duration crosses an hour.
• Use the exit question to identify whether students can calculate a start time independently and explain their strategy.

Differentiation

• Support students with a movable clock, a pre-drawn timeline, and the sentence frame: “I started at ___ and counted forwards ___ minutes to reach ___.”
• Encourage students to make jumps of 5, 10, 15 or 20 minutes before combining them, rather than relying immediately on formal subtraction.
• Pair students strategically and allow oral explanations, drawing or practical clock movements before recording written calculations.
• Extend confident students by asking them to create a run problem with a start time, finish time and duration, including one that crosses midday or midnight within a 24-hour timeline.