Decimal Place
Tenths, hundredths, thousandths — line up the point.
For grown-ups
- How long: 10 to 15 minutes is plenty. Short and frequent beats long and occasional — the early-numeracy trials with the largest effects ran eight weeks or less.
- 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.
- Not timed: thinking time is the point of a book. Let silences run.
- 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
Reading, comparing and adding decimals to thousandths.
Comparison pairs use the durable misconception that a longer decimal is a bigger number — 0.4 against 0.38. It is the decimal cousin of comparing two-digit numbers digit by digit, and it survives a long time unless it is confronted directly.
- The underlying idea
- Decimal place value, and the misconception that a longer decimal is larger.
- Where this sits in Illustrative Mathematics
- 5th grade Unit 5: Place Value Patterns and Decimal Operations · 5th grade Unit 6: More Decimal and Fraction Operations
- Sources
- Illustrative Mathematics / Kendall Hunt (2024) · Holloway et al. (2009) all references →
Related measured skills: ALPACA · Elementary operations, MagPI · Number comparison. What this means