Elapsed time
Calculate elapsed time in Grade 6 math by counting forward from a start time to an end time — work with hours and minutes across AM and PM to solve real-world scheduling problems.
Key Concepts
Property When we calculate the amount of time between two events, we are calculating elapsed time (the amount of time that has passed).
Examples To find the time from 7:15 a.m. to 11:10 a.m., calculate $10:70 7:15 = 3 \text{ hours } 55 \text{ minutes}$. What time is $2\frac{1}{2}$ hours after 10:43 a.m.? $10:43 + 2:30 = 12:73$, which becomes 1:13 p.m. How long is it from 2:10 p.m. to 4:45 p.m.? $4:45 2:10 = 2 \text{ hours } 35 \text{ minutes}$.
Explanation You're a time detective solving a mystery! To find out how long something took, subtract the start time from the end time. If the end minutes are smaller than the start minutes, you must borrow! 'Steal' one hour from the end time and turn it into 60 extra minutes. Now you have enough to solve the problem!
Common Questions
How do you calculate elapsed time?
Count forward from the start time to the end time in steps. First count to the nearest hour, then count remaining minutes. For example, from 2:15 PM to 4:45 PM is 2 hours and 30 minutes elapsed.
How do you handle AM to PM time calculations?
Noon is the changeover point. Count from the start time to 12:00 PM (noon) or 12:00 AM (midnight), then continue counting to the end time. Add the two portions together for total elapsed time.
What are common mistakes with elapsed time problems?
Students often forget that 60 minutes = 1 hour and regroup incorrectly. Also, when crossing noon or midnight, it is easy to count AM as PM. Always write out the start and end times clearly before calculating.
Why is elapsed time an important real-world skill?
Elapsed time is used daily for scheduling, travel planning, cooking, and tracking how long tasks take. Understanding it helps students read timetables, plan their day, and solve practical schedule problems.