Different denominators, mixed numbers, and multiplying fractions by whole numbers — the year fractions get genuinely complex.
25 August 2026 · 6 min read
Every fraction topic up to this point has had a training wheel attached: same denominators only, proper fractions only, no mixed numbers. Year 5 removes most of those restrictions at once, which is exactly why it tends to be the year parents notice fractions becoming genuinely hard.
Adding 1/4 and 1/3 isn't just harder arithmetic — it requires an extra conceptual step that same-denominator addition never needed: recognising that the two fractions are currently measured in different-sized "units" (quarters and thirds), and converting both to a shared unit (twelfths, in this case: 3/12 + 4/12 = 7/12) before the addition makes sense at all. Skipping straight to adding numerators and denominators — the classic 1/4 + 1/3 = 2/7 error — is one of the most well-documented fraction misconceptions across the entire primary curriculum, and it shows up heavily in Year 5 because this is the first time the shortcut of "same denominator" isn't available to fall back on.
Converting 7/2 to 3½ (or back again) is conceptually simple once understood, but it's easy for a child to make a small arithmetic slip in the conversion itself — miscounting how many whole times the denominator fits into the numerator — which then throws off every step that follows, even if the actual fraction method used afterwards is completely correct.
A common point of confusion: multiplying a fraction by a whole number (2/5 × 4) doesn't need a common denominator at all — you're scaling the fraction, not combining two differently-sized fractions. Children who've just spent weeks carefully finding common denominators for addition sometimes apply the same process unnecessarily to multiplication, overcomplicating a problem that didn't need it.
Fraction strips or a simple fraction wall — showing quarters and thirds lined up against a shared twelfths scale — make the "different denominators, same underlying whole" idea visible in a way that pure numbers on a page usually can't. Seeing that 1/4 and 1/3 genuinely occupy different amounts of space, and that twelfths is the smallest scale where both line up exactly, does a lot of the conceptual work that an abstract explanation struggles to do alone.
Grasp Maths checks a wrong fraction answer against the well-documented "add everything" misconception directly, so a mistake like 1/4 + 1/3 = 2/7 gets flagged as exactly what it is, and the next questions target finding common denominators specifically, not fraction addition in general.
Looking for printable practice too? See our Year 5 maths worksheets, or read the full Year 5 maths overview.
Try a free Grasp Maths practice session, matched to the Year 5 curriculum.