Hundred Line Hop
No tick marks this time. Where does 63 go?
For grown-ups
- How long: 5 to 10 minutes is plenty. Short and frequent beats long and occasional — the early-numeracy trials with the largest effects ran eight weeks or less.
- The strategy to reinforce: “Use landmarks” — Fifty is the middle. Twenty-five is halfway to the middle. Work from those. If they stall, remind them of this rather than giving the answer.
- When they get one wrong: the page shows the working. Read it together rather than moving straight on. Feedback that explains is worth several times more than feedback that only marks right or wrong, and that gap is wider in maths than in any other subject.
- On the timer: it is off unless you turn it on, and it is never needed. Use it only once the skill is comfortable, never to introduce it.
- Print it too: doing the same problems on paper a few days later is worth more than doing twice as many today.
What this practises
Estimating where a number sits on a 0–100 line.
The same number line, now without tick marks. Removing them is the point: the child has to reason from landmarks (nought, fifty, one hundred) instead of counting, which is what estimating a magnitude actually is.
- The underlying idea
- Landmark-based estimation rather than counting.
- Where this sits in Illustrative Mathematics
- 2nd grade Unit 4: Addition and Subtraction on the Number Line · 2nd grade Unit 5: Numbers to 1,000
- Sources
- Institute of Education Sciences / What Works Clearinghouse (2021) · Schneider et al. (2018) · Geary (2011) all references →
Related measured skill: MagPI · Number line estimation. What this means