Racing Seconds — Measuring Time
In a race, every second counts! Time can be measured in seconds, minutes, and hours. This chapter helps us read clocks, convert between units of time, and calculate time intervals.
Units of Time
Key formulas
Reading the Clock
- An analogue clock has an hour hand (short) and a minute hand (long).
- A digital clock shows time as hours:minutes (e.g., 3:45).
- The minute hand moves one full circle every 60 minutes.
- Each small division on a clock = 1 minute; each number = 5 minutes.
Converting Time
To convert minutes to seconds, multiply by 60.
To convert hours to minutes, multiply by 60.
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A race takes 2 minutes and 35 seconds. How many seconds is that?
2 min = 120 s. Total = 120 + 35 = 155 seconds
Pooja starts a game at 4:15 and finishes at 4:48. How long did she play?
Time = 48 - 15 = 33 minutes
A programme starts at 6:30 p.m. and lasts 1 hour 45 minutes. When does it end?
6:30 + 1 h = 7:30. 7:30 + 45 min = 8:15 p.m.
A train leaves at 10:20 a.m. and arrives at 1:05 p.m. How long is the journey?
10:20 to 1:05 = 2 hours 45 minutes.
Convert 3 hours 20 minutes to minutes.
3 x 60 = 180. Total = 180 + 20 = 200 minutes
Common mistakes
- Forgetting that there are 60 (not 100) minutes in an hour.
- Mixing up a.m. and p.m. when calculating time intervals that cross noon or midnight.
Summary
Time units: 60 s = 1 min, 60 min = 1 h, 24 h = 1 day. To find time intervals, subtract start time from end time. Always check whether the time crosses noon.