--- title: "Bar charts and time graphs" description: "Interpret and present discrete and continuous data using appropriate graphical methods, including bar charts and time graphs" canonical: https://lightmysky.com/learn/mathematics/bar-charts-and-time-graphs-mt_ChjMU2GDJa source: https://lightmysky.com/learn/mathematics/bar-charts-and-time-graphs-mt_ChjMU2GDJa.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Bar charts and time graphs Interpret and present discrete and continuous data using appropriate graphical methods, including bar charts and time graphs Subject: Mathematics · Area: Data & Statistics · Ages 8 to 9 Page: https://lightmysky.com/learn/mathematics/bar-charts-and-time-graphs-mt_ChjMU2GDJa ## Ready when they can - Read a time graph showing temperature changes over a day - Present data about plant growth over weeks as a time graph - Choose a bar chart for comparing categories or a time graph for measurements recorded over time, and explain the choice ## Lesson: Bar charts and time graphs You have read bar charts before. Each bar shows a value for one category. Bars help you compare separate groups, such as favourite colours. *(drawing: Each colour has its own bar. Blue has the most votes.)* A time graph can show measurements taken over time. Put time along the bottom and the measured value up the side. Label both axes and include units. Mark each reading where its time and value meet, then join the points in time order. Equal time gaps need equal spaces. **Example.** A plant measures 2 cm in week 1, 5 cm in week 2 and 9 cm in week 3. For its time graph, put weeks along the bottom and height in centimetres up the side. Plot the three readings and join them. These cells list the readings; they are not a time graph. To read a time graph, find the time along the bottom. Move up to its point, then across to the value scale. Compare two readings to find whether the value rose, fell or stayed the same. Find the highest and lowest readings before finding their difference. Compare recorded values: a larger number means a higher reading. Joined points help you follow changes but do not reveal unrecorded values between readings. Separate bars can also show readings at particular times. Joined points often make the pattern easier to follow. Counts, such as daily visitors, can change over time too. **Example.** A plant grows from 4 cm to 10 cm. Subtract the earlier height from the later height: 10 - 4 = 6 cm. If it first grows to 7 cm and then to 10 cm, its total growth is still 6 cm. The number line shows the height difference, not a time graph. **Recap.** Bars compare categories. Time graphs connect readings in time order. Label the axes, use equal spacing and separate recorded values from values you do not know. *This lesson, question bank and flashcards were written for this dataset.* ## Practice 18 questions on this page, each with its working shown. ## Needs first - [Scaled picture graphs and bar graphs](https://lightmysky.com/learn/mathematics/scaled-picture-graphs-and-bar-graphs-mt_r8XnXwRA6g) - [Data collection and display vocabulary](https://lightmysky.com/learn/mathematics/data-collection-and-display-vocabulary-mt_u5HkSxZECM) ## Opens up - [Statistical analysis vocabulary](https://lightmysky.com/learn/mathematics/statistical-analysis-vocabulary-mt_fmm-P17Vka) - [Reading and comparing bar and line graphs](https://lightmysky.com/learn/mathematics/reading-and-comparing-bar-and-line-graphs-mt_H6LlpWgEYS) - [Graphing seasonal weather data](https://lightmysky.com/learn/science/graphing-seasonal-weather-data-mt_NYsz6QgaaE) - [Recording data with diagrams and graphs](https://lightmysky.com/learn/science/recording-data-with-diagrams-and-graphs-mt_rDjtmDogJr) - [Tables, charts, and graphs](https://lightmysky.com/learn/science/tables-charts-and-graphs-mt_YHsUhi4Prc)