Elapsed time problems
Solve word problems involving elapsed time by adding and subtracting time intervals in minutes, including using a number line
What a learner can do afterwards
- 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
1 · Read
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.
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.
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.
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.
Hop forward on a number line by the elapsed minutes, and friendly chunks make big jumps easy to count.
2 · Watch
Take it off screen
Where it sits
Where this leads
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.