Elapsed time is the duration between a start time and end time. From 2:15 PM to 2:45 PM, 30 minutes have elapsed. Students count on by 5s or 1s on a clock face, or subtract end time from start time, to find elapsed time within one hour.
You already know how to read times to five-minute intervals — you can look at a clock and say "it is 2:15" or "it is 2:45." Elapsed time asks a different question: not *what time is it*, but *how long did something take*? The difference between a start time and an end time is the elapsed time, and it is measured in minutes (or hours and minutes for longer durations).
The most reliable strategy is counting on using the clock face. Imagine the minute hand starting at 2:15. You want to reach 2:45. Count by 5s as the minute hand sweeps forward: 2:15 → 2:20 → 2:25 → 2:30 → 2:35 → 2:40 → 2:45. That is 6 hops of 5 minutes each: 6 × 5 = 30 minutes elapsed. You can also use a number line, marking the start time at one end and hopping forward in jumps of 5 or 10 until you reach the end time.
A second strategy is subtraction. If start is 2:15 and end is 2:45, subtract the minutes: 45 − 15 = 30 minutes. This works cleanly when both times share the same hour. Be careful if the minutes would require borrowing (e.g., 3:05 to 3:52) — in those cases, counting on is often easier and less error-prone.
The key concept to hold onto is that elapsed time is a duration, not a clock reading. When you say "30 minutes passed," you are describing how long something lasted, not pointing to a moment in time. This distinction becomes essential when you later work with problems that cross the hour mark — knowing whether you are tracking a position on a clock versus an amount of time is what keeps the reasoning straight.
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