When will we finish?
Add a duration to find a finishing time and its day.
Explore this lesson →12 practice questions · Optional read aloud · Thinking pad
Let’s understand the idea.
- Separate a starting time, an ending time and the duration between them. A time is a point; a duration is a length of time.
- Use equal minute intervals on a number line. You may break a duration into convenient jumps, such as reaching the next hour first.
- Count forward to find a finish and backward from a finish to find a start. Noon changes a.m. to p.m.; midnight begins a new day. The elapsed line keeps going when the clock wraps.
Something to notice
Ask the learner to measure a real activity in minutes and solve an unfamiliar start/end/duration story with a number line or an explanation. Simulated timings do not validate practical clock use. The API checks exact minutes and both time-of-day and named day, and accepts different valid positive jump decompositions. Our two named days and 180-minute explorer are authored bounds, not limits in the standard.
Try it. Change it. Explain it.
Open the lesson to use its pictures and controls. In How it works, connect the picture to the idea. In Play & discover, change the quantities and notice what stays the same. In Your turn, answer questions and use the explanation to check your reasoning.
You can ask for help, draw on the thinking pad, or listen to the question and answer options. Progress distinguishes independent work from work completed with help.
Let’s try it →Curriculum connection
Grade 3 · 3.MD · US Common Core
This lesson is mapped to these standards. A completed activity is practice evidence, not a claim of mastery. Content is checked against the linked official standards and its mathematical models are tested.