--- title: "Elapsed time problems" description: "Solve word problems involving elapsed time by adding and subtracting time intervals in minutes, including using a number line" canonical: https://lightmysky.com/learn/mathematics/elapsed-time-problems-mt_IL86kadLSS source: https://lightmysky.com/learn/mathematics/elapsed-time-problems-mt_IL86kadLSS.md retrieved: 2026-09-02 --- > **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`. # Elapsed time problems Solve word problems involving elapsed time by adding and subtracting time intervals in minutes, including using a number line Subject: Mathematics · Area: Measurement · Ages 8 to 9 Page: https://lightmysky.com/learn/mathematics/elapsed-time-problems-mt_IL86kadLSS ## Ready when they can - A film starts at 2:15 and lasts 47 minutes — when does it end? - Calculate how many minutes between 9:20 and 10:05 - Use a number line to show the elapsed time between two events ## Lesson: Elapsed time problems A number line can show time passing. Start at the beginning time, then hop forward by the number of minutes that pass. Wherever you land is the end time. *(drawing: A film starts at 2:15 and lasts 47 minutes. Hop 5 minutes to 2:20, then 40 minutes to 3:00, then 2 more minutes to 3:02.)* **Example.** To add 47 minutes to 2:15, break the jump into friendly pieces. First hop 5 minutes to reach 2:20. Then hop 40 minutes to reach 3:00. A clock's minutes stop at 59, so that hop lands on 3:00 and never on 2:60. Then hop the last 2 minutes to land on 3:02. **Example.** To find the minutes between 9:20 and 10:05, hop forward from 9:20 to 10:00. That is 40 minutes. Then hop 5 more minutes to reach 10:05. So 40 minutes plus 5 minutes is 45 minutes in total. **Tip.** When the jump is large, hop to a friendly number first, like the next ten or the next hour. Small hops are easier to count than one big jump. **Recap.** Hop forward on a number line by the elapsed minutes, and friendly chunks make big jumps easy to count. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Comparing Time Durations](https://lightmysky.com/learn/mathematics/comparing-time-durations-mt_4emC463IyW) - [Telling time to the minute (age 8+)](https://lightmysky.com/learn/mathematics/telling-time-to-the-minute-age-8-mt_UNzojLkNdm) ## Opens up - [Telling time to the minute (age 9+)](https://lightmysky.com/learn/mathematics/telling-time-to-the-minute-age-9-mt_2yas4Unc8o) - [Choosing mathematical tools](https://lightmysky.com/learn/mathematics/choosing-mathematical-tools-mt_d-WZC2OyMB)