A free guide from Water Warriors · Updated 2026-07-30
Number bonds are the pairs of numbers that add together to make a total. Knowing them by heart is the quiet engine behind fast, confident mental maths.
What is a number bond?
A number bond is simply a pair (or group) of numbers that combine to make a
given total. The bonds to 10, for example, are 0+10, 1+9, 2+8, 3+7, 4+6 and 5+5.
"Knowing your bonds to 10" means being able to answer, instantly, "7 and what
makes 10?" without counting.
Why they matter so much
Bonds to 10 and 20 are the building blocks of almost every mental strategy that
comes later:
Adding past ten: to work out 8 + 5, a child who knows 8 + 2 = 10
splits the 5 into 2 and 3, makes ten, then adds the 3 → 13. This "make ten"
strategy is far faster and more reliable than counting on fingers.
Subtraction: bonds work both ways. Knowing 6 + 4 = 10 instantly
gives 10 − 4 = 6.
Bigger numbers: bonds to 100 (e.g. 30 + 70, 45 + 55) power
mental subtraction and giving change.
Column methods: children who know their bonds carry and
exchange far more smoothly.
How to teach them
Part–whole thinking
Draw a "part–whole" model: a circle for the whole (say 10) with two circles below
for the parts. Fill in one part and ask for the other. This shows that a number
can be split in many ways, all of which still make the whole.
Ten frames
A ten frame is a 2 × 5 grid. Put five counters in and it's obvious you need five
more to fill it — the bond to 10 becomes something children can see,
not just recite. Buttons, pasta or coins in an egg-box work just as well at home.
Fingers, properly
Fingers aren't cheating — they're a child's first number line. Hold up seven
fingers and it's clear three are down: 7 and 3 make 10. The aim is to use the
image often enough that the fact is remembered without the fingers.
A sensible progression
Bonds within 5, then to 5 (ages 4–5).
Bonds to 10 — the big one — until they are instant (ages 5–6).
Bonds to 20, and the related subtraction facts (ages 6–7).
Multiples-of-ten bonds to 100, e.g. 40 + 60 (age 7+).
Bonds to 100 with any numbers, e.g. 63 + 37 (age 7–8).
Aim for instant, not just correct. A child who has
to count up to find 6 + 4 hasn't secured the bond yet. Quick daily recall is what
turns it from a sum into a known fact.
Quick activities
"Make 10" snap: with a pack of cards (ace = 1, picture cards removed), take turns turning cards over and shout "snap!" when two on the table make ten.
Bond ping-pong: you say a number, they say its partner to ten (or twenty), as fast as you can go.
Hidden counters: show ten counters, cover some, and ask how many are hidden.
Screen practice: games that fire quick bond questions get lots of repetitions in painlessly.
In Water Warriors, children answer rapid number questions — including bonds and
quick addition — between bursts of play. Try it free.