Exchanging in subtraction, mixing up sharing and grouping, and times tables that haven't quite become automatic yet.
25 August 2026 · 5 min read
Year 2 introduces a few genuinely harder ideas — exchanging, formal times tables, fraction equivalence — so it's also the year where a handful of very specific, well-known mistakes start showing up. Here's what to look out for.
Given 42 − 17, a child who hasn't yet secured exchanging will often subtract the smaller digit from the larger one in each column regardless of which number it belongs to: 7 − 2 = 5 in the units column, then 4 − 1 = 3 in the tens column, giving 35 instead of the correct answer, 25. This is one of the best-documented subtraction misconceptions at this age, and it almost always points to a place value gap underneath, not a subtraction gap — the child hasn't yet grasped that a ten can be broken into ten ones to make the subtraction possible.
A child practised mainly on "share 12 sweets between 4 people" questions can genuinely struggle with "how many groups of 4 can you make from 12 sweets?" — even though both give the same answer, 3. The confusion is about recognising which real-world situation the question describes, not about the division fact itself.
Asked "what's 5 × 6?", a child who counts "5, 10, 15, 20, 25, 30" under their breath before answering is getting the right answer through a slower route than the one Year 2 is aiming for. It's not wrong, but it's a sign the fact isn't fully secure yet — worth noting rather than ignoring, since it tends to slow a child down noticeably once questions get more complex.
Because 2/4 and 1/2 look like different fractions on the page, some children resist the idea that they're the same amount, even after seeing it demonstrated with a shape cut in half versus a shape cut into quarters with two shaded in. This is a genuinely new kind of thinking for most seven-year-olds — that two different-looking things can be mathematically identical — and it's worth revisiting with physical objects rather than expecting it to click from a single explanation.
"Quarter past" and "quarter to" are commonly swapped, and children sometimes answer a time question correctly on an analogue clock but then struggle to write it the same way digitally, or vice versa — the two formats don't automatically transfer for every child at this stage.
As with Year 1, the key is watching for a pattern rather than reacting to a single wrong answer — the same type of mistake showing up more than once, on similar questions, days or weeks apart. At that point, it's worth stepping back to the specific underlying skill (place value for exchanging, equivalent fraction concepts, or straight times-table recall) rather than simply repeating more questions at the same level.
Grasp Maths checks a wrong answer against exactly these kinds of well-documented Year 2 misconceptions, so a "smaller from larger" subtraction slip gets flagged as a place value issue, not just marked wrong and moved past.
Looking for printable practice too? See our Year 2 maths worksheets, or read the full Year 2 maths overview.
Try a free Grasp Maths practice session, matched to the Year 2 curriculum.