Primary 1 Measurement (Length and Time)
Measure one object with a ruler, then use clock hands and everyday events to understand time.
Keywords
Point to the ruler or clock as you use these words.
- Length
- How long an object is.
- Centimetre (cm)
- A unit used to measure a short length with a ruler.
- Ruler
- A tool with marks for measuring length; line up the object with 0.
- Hour hand
- The shorter clock hand that shows the hour.
- Minute hand
- The longer clock hand that shows the minutes.
- a.m. / p.m.
- a.m. is before noon; p.m. is from noon to before midnight.
- Duration
- How long an event lasts.
- Half an hour
- 30 minutes.
Measure length
Length tells us how long an object is. Line up one end with 0 cm, keep the ruler straight, and read the centimetre mark at the other end.
How long is the pencil?
Parent prompt: “Which mark is under the pencil’s first end? Which mark is under its other end? What unit do we say?”
Common mistake: Starting to count at the ruler’s edge instead of the 0 cm mark. Make both ends line up with the marks before reading.
Read the time
The short hand shows the hour. The long hand shows the minutes. At 12 it is “o’clock”; at 6 it is “half past”.
What time does the clock show?
Parent prompt: “Which hand is longer? Where is it pointing? Where is the shorter hand?”
Common mistake: Saying 6:15 when the long hand points to 6. Each number is five minutes; the 6 means 30 minutes.
Understand a.m. and p.m.
A clock face can show 7:00 in both the morning and evening. The event tells us which one: a.m. runs from midnight to before noon; p.m. runs from noon to before midnight.
It is time for breakfast. Is this a.m. or p.m.?
Parent prompt: “Could the same clock face show dinner time too? What changes in the story?”
Common mistake: Trying to find a.m. or p.m. from the hands alone. The hands show the same position at 7 a.m. and 7 p.m.; use the time of day.
Duration: one hour and half an hour
Duration is how much time passes between a start and an end. Watch where the minute hand travels, and check how far the hour hand moves.
How much time passes from the first clock to the second?
Parent prompt: “Where did the long hand begin and end? Did it travel half a turn or a full turn?”
Common mistake: Calling 2:00 to 2:30 one hour because the minute hand moved to 6. That is only half a turn: 30 minutes, or half an hour.