Today is rung 7 of 7 on this topic
Elapsed time, measurement and scaled graphs
Can do: Works out how long something took, measures in the right unit, and reads a graph where one square equals five.
Why it matters
Elapsed time is the most-used and least-taught bit of school maths, and scaled graphs are where most data misreadings begin.
What it looks like when it's wobbly
Subtracts times as if they were decimals — 3:15 to 4:05 becoming "90 minutes" — and counts bars rather than reading the scale.
⏱️ Two-minute check
"It started at 2:40 and finished at 3:25. How long?" Then read a graph scaled in fives.
Solid looks like: 45 minutes, and a graph value read correctly off the scale.
The full activity for this topic · 15 minutes
Number Line Time
- 1Draw an empty number line and mark the start time on the left.
- 2Jump to the next o'clock, write the minutes on the jump, then jump to the end.
- 3Add the jumps. This beats column subtraction for time every single time.
- 4Do three real ones: journey times, cooking times, screen time.
- 5Find a real graph and ask three questions, at least one needing the scale.
If it's too hard
Times within the same hour.
If it's too easy
Crossing midday or midnight, and working backwards from an end time.
Say this
"Don't subtract clock times like ordinary numbers. Jump to the next o'clock first."