Decimal Drop
Where does 0.35 land? And what fraction is that?
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: “Tenths first” — The first digit after the point is tenths. 0.35 is between three tenths and four tenths. 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
Placing a decimal between 0 and 1, and matching it to its fraction.
Decimals and fractions on the same number line, so they read as one idea in two notations rather than two unrelated topics. Matching 0.25 to a quarter is the link that makes both easier.
- The underlying idea
- Decimals and fractions as one idea in two notations, on one line.
- Where this sits in Illustrative Mathematics
- 4th grade Unit 4: From Hundredths to Hundred-thousands
- Sources
- Institute of Education Sciences / What Works Clearinghouse (2021) · Schneider et al. (2018) · Riconscente (2013) all references →
Related measured skills: MagPI · Number line estimation, ALPACA · Elementary operations. What this means