Time
Third-grade students often struggle with elapsed time problems, making errors when adding hours and minutes across different time formats. Teaching time concepts requires structured practice with clock faces, number lines, and real-world scenarios that connect to students' daily experiences.
Why it matters
Time skills appear constantly in students' lives—from calculating when the school bus arrives to determining how long recess lasts. CCSS.3.MD standards emphasize telling time to the nearest minute and solving elapsed time problems because these abilities support mathematical reasoning and practical independence. Students use time calculations when planning homework schedules, figuring out TV show durations, or understanding sports game lengths. A baseball game lasting 2 hours 45 minutes starting at 1:15 PM ends at 4:00 PM—this type of problem-solving transfers to scheduling family activities, calculating travel times, and managing personal routines. Mastering time conversions (like knowing 90 minutes equals 1 hour 30 minutes) builds number sense and prepares students for more complex mathematical concepts involving rates, ratios, and proportional reasoning in later grades.
How to solve time
Time
- 60 seconds = 1 minute; 60 minutes = 1 hour; 24 hours = 1 day.
- To convert hours to minutes: multiply by 60.
- Elapsed time: count forward from start to end.
- 24-hour clock: add 12 to pm hours (e.g. 3 pm = 15:00).
Example: 2 h 30 min = 2 × 60 + 30 = 150 minutes.
Worked examples
How many minutes in 1 hour?
Answer: 60
- Recall the time fact → 60 — Think of the minute hand going all the way around the clock once. It passes 60 tiny marks -- one for each minute.
- State the answer clearly → There are 60 minutes in 1 hour — The answer is 60. This is a basic time fact worth memorising, just like knowing there are 10 fingers on your hands.
School starts at 7:00 AM. The school day lasts 3 hours. What time does school end?
Answer: 10:00 AM
- Read the starting time → Start: 7:00 AM — We begin at 7:00 AM. Think of where the hour hand is pointing on a clock.
- Count 3 hours forward → 7 + 3 = 10 — Add 3 to the hour: 7 + 3 = 10.
- Write the final time → 10:00 AM — The answer is 10:00 AM. On a 24-hour clock, that's 10:00.
A birthday party starts at 6:15 PM and lasts 1 hour 15 minutes. When does it end?
Answer: 7:30 PM
- Read the starting time → Start: 6:15 PM — The event begins at 6:15 PM. Write down the start hour (18) and start minutes (15) separately.
- Add the hours first → 18:15 + 1h = 19:15 — Adding hours is easy -- just move the hour hand forward by 1. We go from hour 18 to hour 19.
- Add the minutes → 15 + 15 = 30 min — Add 15 minutes to 15: 15 + 15 = 30. This is less than 60, so no carrying needed.
- Combine into final time → 7:30 PM — The event ends at 7:30 PM. Think of it like this: 6:15 PM plus 1 hour 15 minutes lands you at 7:30 PM.
Common mistakes
- Students confuse 24-hour and 12-hour formats, writing 3:00 PM as 3:00 instead of 15:00, or converting 14:30 to 2:30 AM instead of 2:30 PM.
- When adding time, students forget to carry minutes over the 60-minute mark, calculating 2:45 + 30 minutes as 2:75 instead of 3:15.
- Students subtract time incorrectly without borrowing, finding elapsed time from 1:15 to 2:05 as 1 hour 10 minutes instead of 50 minutes.
- Converting hours to minutes causes errors when students add instead of multiply, writing 3 hours as 3 + 60 = 63 minutes instead of 3 × 60 = 180 minutes.