Find Elapsed Time Across an Hour

Supplied materials

• Paper and a pencil; drawing and spoken explanations are welcome. An adult may read directions and options aloud.
• Supplied worked-case record: From 1:48 to 2:17, twelve minutes reach 2:00 and seventeen more reach 2:17.
• All quantities and shape descriptions are supplied in the worked example and questions; no purchase or personal information is needed.

Learn the idea

Elapsed time is a duration, not a clock label. When a start and finish cross an hour, split the duration at the hour boundary. Add minutes up to the boundary and minutes after it. This avoids subtracting clock digits as if every hour contained one hundred minutes.

Read the supplied start and finish on the same afternoon. Jump to the next whole hour, then to the finish. Add the minute jumps and check by advancing that duration from the starting clock time.

An hour contains sixty minutes. Do not subtract colon-free clock labels as ordinary base-ten numbers. Draw a timeline with a whole-hour stop between the start and finish.

1. Draw a timeline with a whole-hour stop between the start and finish.
2. Follow the worked example. Point to each number or shape feature and say what it tells you.
3. Read the supplied start and finish on the same afternoon.
4. Try the question and then the three practice questions. Check your answers and explain any change you make.

Check your reasoning

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Take it further

From 9:37 to 10:14 on the same morning: expected 37 minutes.

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