📋 In This Article
- Mistake 1: Treating digits as individual numbers
- Mistake 2: Removing zero placeholders
- Mistake 3: Confusing tens and ones columns
- Mistake 4: "More digits = bigger number" with decimals
- Mistake 5: Misreading large numbers by period
- Mistake 6: Rounding the wrong digit
- Mistake 7: Writing expanded form with zeros included
After working through thousands of student answers, the same mistakes appear again and again. The good news: each one has a clear cause and a specific fix. Identifying which mistake a child is making is the first step to fixing it quickly.
Mistake 1: Treating digits as individual numbers
What it looks like
A child reads 47 as "four seven" instead of "forty-seven." When asked the value of the 4, they say "four" instead of "forty." They treat the number as two separate single digits rather than one structured whole.
This mistake is very common in Grade 1 and early Grade 2. It's not a sign of low ability — it's simply what happens when children learn to count before they learn about number structure. The fix is consistent language correction, every day, until it becomes automatic.
Mistake 2: Removing zero placeholders
What it looks like
A child writes 305 as "35" or reads it as "thirty-five." They treat the zero as unimportant — "it's just nothing." Similarly, 4,070 becomes "470" and 0.306 becomes "0.36."
⚠️ This mistake causes cascading errors
A child who removes zero placeholders will also make errors in addition (misaligning columns), subtraction (wrong borrowing), and reading/writing large numbers. Fix it early — it does not self-correct.
Mistake 3: Confusing which column is tens and which is ones
What it looks like
In the number 73, the child says the 3 is worth 30 and the 7 is worth 7. They know tens and ones exist but have the columns backwards.
Mistake 4: "More digits = bigger number" with decimals
What it looks like
A child thinks 0.85 > 0.9 because 85 is bigger than 9. They apply whole-number logic to decimals. This is one of the most persistent mistakes in upper primary maths.
🎯 The money analogy
£0.90 is 90 pence. £0.85 is 85 pence. Which would you rather have? Children always get money comparisons right — then you can connect it back to the decimal representation.
Mistake 5: Misreading large numbers by period
What it looks like
A child reads 4,200,000 as "four thousand, two hundred" — ignoring the millions period. Or they read 52,000 as "fifty-two thousand" correctly but stumble on 520,000 (five hundred and twenty thousand).
Mistake 6: Rounding the wrong digit
What it looks like
Asked to round 4,763 to the nearest 100, a child changes the tens digit (giving 4,760) or changes the hundreds digit based on the ones digit (giving 4,800 because "3 is small") rather than looking at the tens digit.
Mistake 7: Including zeros in expanded form
What it looks like
A child writes 4,308 in expanded form as 4,000 + 300 + 0 + 8. Including the "+ 0" is technically not wrong, but it is non-standard and usually indicates the child doesn't understand that zero contributes nothing to the total.
💡 Diagnosis tip for parents and teachers
To quickly identify which mistakes a child is making, give them these three tasks: (1) Write 5,060 in expanded form. (2) Compare 0.4 and 0.38. (3) Round 3,850 to the nearest 100. Their answers will reveal mistakes 2, 4, and 6 instantly.
🔧 Use these tools to fix the mistakes
Our free interactive tools let children see exactly where each digit sits — which fixes most of the mistakes above on the spot.