Grade 6 Mathematics Measurements – Time Notes
Mathematics — Measurements
Subtopic: Time (for age 11, Kenya)
Time helps us know when things happen and how long they take. Below are the important ideas, simple rules, examples and practice problems you can use at school or at home.
1. Units of time (small → large)
- 1 minute = 60 seconds
- 1 hour = 60 minutes
- 1 day = 24 hours
- 1 week = 7 days
2. Converting between units — easy steps
To convert: multiply when going to a smaller unit, divide when going to a larger unit.
- Convert 2 hours to minutes: 2 × 60 = 120 minutes.
- Convert 150 seconds to minutes and seconds: 150 ÷ 60 = 2 remainder 30, so 150 s = 2 min 30 s.
- Convert 2 h 15 min to minutes: 2×60 + 15 = 120 + 15 = 135 minutes.
3. Reading clocks
There are two main types: digital and analogue.
Analogue clock: The short hand shows the hour. The long hand shows minutes.
Digital clock: Shows time like 07:30 or 14:15. Use AM/PM or a 24-hour clock.
4. AM/PM and 24-hour clock (useful for trains, schedules)
- AM = morning (midnight to noon). PM = afternoon/evening (noon to midnight).
- 24-hour time: 1:00 PM = 13:00, 6:30 PM = 18:30, midnight = 00:00 or 24:00.
5. Elapsed time — how long between two times
Steps:
- If times are not on the hour, use minutes. It helps to add to the next hour, then continue.
- You can use a number line: count hours then minutes, or convert both times to minutes and subtract.
School starts at 08:00 and ends at 15:30. How long is the school day?
Method 1 — hours and minutes: From 08:00 to 15:00 = 7 hours. From 15:00 to 15:30 = 30 minutes. Total = 7 h 30 min.
Method 2 — convert to minutes: 08:00 = 8×60 = 480 min. 15:30 = 15×60 + 30 = 930 min. Difference = 930 − 480 = 450 min = 7 h 30 min.
6. Useful tips for exams and tests
- Remember 60 seconds in a minute and 60 minutes in an hour. Use multiplication/division by 60.
- When finding elapsed time that crosses noon or midnight, be careful with AM/PM or use the 24-hour clock.
- Draw a simple timeline: mark the start, count full hours, then minutes.
7. Practice questions (try these)
- Convert 3 hours 40 minutes into minutes.
- How many minutes are there in 2 hours 5 minutes?
- A matatu leaves town at 06:25 and arrives at 08:10. How long is the journey?
- Convert 1500 seconds into minutes and seconds.
- If a lesson starts at 10:35 and lasts 45 minutes, what time does it finish?
- Change 7:20 PM into 24-hour time.
8. Answers
- 3 h 40 min = 3×60 + 40 = 220 minutes.
- 2 h 5 min = 2×60 + 5 = 125 minutes.
- 06:25 → 08:10. From 06:25 to 07:25 = 60 min. From 07:25 to 08:10 = 45 min. Total = 105 minutes = 1 h 45 min.
- 1500 ÷ 60 = 25 remainder 0 → 25 minutes 0 seconds (1500 s = 25 min).
- 10:35 + 45 min = 11:20 (add 25 min to reach 11:00 then +20 min → 11:20).
- 7:20 PM = 19:20 in 24-hour time.
- Bus timetable: If a bus leaves Nairobi at 13:15 and arrives in Nakuru at 16:40, how long was the trip?
- Homework planning: You have 30 min Maths, 45 min English and 20 min Science. How long will you study?
Keep practising reading both analogue and digital clocks. Use the conversion tricks often — they help a lot in the exam.