Strong mental maths isn't really about memorising more facts — it's about having a small set of genuinely flexible strategies that make calculation faster and more reliable. Here are the ones worth teaching explicitly.
Rounding and adjusting for addition
Adding 99 to something? Round to 100, add, then subtract 1. 47 + 99 becomes 47 + 100 - 1 = 146. This genuinely simple trick makes awkward-number addition far faster than adding the actual ugly number directly.
Doubling and halving for multiplication
Multiplying by 4? Double twice. Multiplying by 8? Double three times. This breaks an unfamiliar multiplication into a sequence of simpler, more familiar doubling steps that most children find genuinely easier than the original calculation.
Using known facts to derive unknown ones
If a child confidently knows 5 x 6 = 30, they can derive 6 x 6 by simply adding one more 6 (36) — genuinely useful for building the harder times tables from ones already secure, rather than treating each fact as entirely separate.
Breaking numbers apart (partitioning)
47 + 35 becomes (40+30) + (7+5) = 70+12 = 82. Splitting numbers into tens and units before adding is genuinely how most confident mental mathematicians actually calculate, rather than trying to hold the whole calculation in mind at once.
Compensation for subtraction
82 - 29 becomes 82 - 30 + 1 = 53. Subtracting a "friendlier" rounded number, then adjusting back, is genuinely faster and less error-prone than subtracting the original awkward number directly.
Why teaching strategies matters more than drilling raw facts
A child with a genuine toolkit of these strategies can work out an unfamiliar calculation confidently, rather than being stuck when a fact hasn't been directly memorised. This flexible number sense is exactly what's tested in the "reasoning" style questions on KS2 SATs, not just raw recall.
How to practise these at home
Rather than teaching all five at once, introduce one strategy at a time, and explicitly point it out during everyday mental maths — "look, I just used the rounding trick there" — so your child sees these as genuine tools to reach for, not just abstract classroom content.
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