Materials & Prep
Prepare a classroom number line from 10:00 to 12:00 marked in 5-minute intervals, plus individual blank number-line strips and pencils. Write the times 10:45 and 11:20 where students can see them. No special materials beyond the usual classroom setup are needed.
Opening: Predict and Notice
DisplayShow 10:45 and 11:20. Ask, "How many minutes pass from 10:45 to 11:20?" Students first record a prediction and circle whether they think the answer is 25, 35, or 75 minutes. Do not confirm the answer yet.
ConnectAsk students to recall what the minute hand does in one hour and how many minutes are in an hour. Have students point to 10:45 and 11:00 on the classroom number line. Accept a spoken answer, a point, or a quick drawing, then say, "Today we will use jumps on a number line so the hour change does not trick us."
Mini-lesson and modeling: Split at the Hour
ModelDraw a number line with 10:45, 11:00, and 11:20. Explain that the elapsed time is the total length of the jumps, not the result of subtracting the minute numbers by themselves.
Think aloud"I start at 10:45. First I jump to the next hour, 11:00. That jump is 15 minutes because 60 - 45 = 15. Then I jump from 11:00 to 11:20. That jump is 20 minutes. I add the two parts: 15 + 20 = 35 minutes. So 35 minutes pass from 10:45 to 11:20."
ConfrontShow the tempting mistake 20 - 45 = -25 and ask why a negative elapsed time cannot describe moving forward from 10:45 to 11:20. Then show the correct split: 10:45 to 11:00 is 15 minutes, and 11:00 to 11:20 is 20 minutes. Emphasize that the hour mark is a stopping point on the number line, not an extra hour to add.
Check for understandingAsk students to draw only the two jumps for 10:50 to 11:15 on their strips and hold them up. Listen for 10 minutes to 11:00 and 15 minutes to 11:15. Ask one student to explain why the answer is 25 minutes rather than 65 minutes.
Guided practice: Build the Jumps Together
ModelWork through 9:35 to 10:10 with students. Prompt, "What is the first destination?" Guide them to mark 10:00, then complete the sentence frame: "From 9:35 to 10:00 is minutes. From 10:00 to 10:10 is minutes. The total is minutes."
ExpectedStudents should find 25 minutes to the hour, 10 minutes after the hour, and 35 minutes altogether. Record the equations 60 - 35 = 25, 10 - 0 = 10, and 25 + 10 = 35.
Turn and talkPartners solve 11:40 to 12:05 using the same frame. Each partner points to the first jump and explains it before the other partner gives the second jump.
Check for understandingAsk students to show a thumb up if the first jump is 20 minutes, a sideways thumb if they need to revise, and then show the number line. Call on students to justify the two parts. Confirm that 12:00 - 11:40 is 20 minutes, 12:05 - 12:00 is 5 minutes, and 20 + 5 = 25 minutes.
ScaffoldKeep this four-step checklist visible: 1. Start at the beginning time. 2. Jump to the next hour. 3. Jump from the hour to the ending time. 4. Add the jumps. Students may use the marked classroom number line and the sentence frame instead of solving mentally.
Collaborative problem set: Minute-Interval Number Lines
Have students work in pairs on individual number-line strips. For each problem, they must mark the hour boundary, label both jumps, write an addition equation, and explain one step to a partner. Give students the checklist from guided practice. Partners alternate as drawer and explainer, then switch roles.
Problem set
- Find the elapsed time from 10:45 to 11:20.
- Find the elapsed time from 2:50 to 3:15.
- Find the elapsed time from 8:25 to 9:05.
- Find the elapsed time from 1:55 to 2:30.
Expected: The answer record is
- 10:45 to 11:00 is 15 minutes; 11:00 to 11:20 is 20 minutes; 15 + 20 = 35 minutes.
- 2:50 to 3:00 is 10 minutes; 3:00 to 3:15 is 15 minutes; 10 + 15 = 25 minutes.
- 8:25 to 9:00 is 35 minutes; 9:00 to 9:05 is 5 minutes; 35 + 5 = 40 minutes.
- 1:55 to 2:00 is 5 minutes; 2:00 to 2:30 is 30 minutes; 5 + 30 = 35 minutes.
CirculateAsk, "Where is your hour boundary?" and "What does this jump represent?" If a pair subtracts the minute numbers directly, have them return to the number line and count from the starting time to the hour before counting beyond it.
ExtensionStudents ready for a challenge create a start time ending in 45 or 50 and an ending time in the next hour, then solve it with two labeled jumps and trade with another pair. The creator must check the partner's jumps by adding them.
Closing check: Explain One Number Line
Exit ticketSolve 4:45 to 5:25. Draw or describe the two jumps, write an addition equation, and complete the sentence: "The elapsed time is minutes because ."
ExpectedStudents should show 4:45 to 5:00 as 15 minutes and 5:00 to 5:25 as 25 minutes, then write 15 + 25 = 40 minutes. Collect the ticket to check both the representation and the explanation.