Number bonds to 100
Worksheet + game · PDF · free
Bonds to 100 use the same logic as bonds to 10, but with tens. If 3 + 7 = 10, then 30 + 70 = 100 and 35 + 65 = 100. Partition into tens and ones when needed: 35 + 65 splits into 30 + 60 and 5 + 5. Number lines marked in tens help. These bonds support mental addition and subtraction with two-digit numbers, change from £1, and estimating. Children should see 100 as ten tens, not a disconnected target. Link explicitly back to bonds to 10 and 20.
Worked example
Find the pair for 35 to make 100. The ones must make 10: 5 + 5. The tens must make 90: 30 + 60. So 35 + 65 = 100.
Watch for this
Adding to 100 by counting in ones — 36, 37, 38 — or mixing tens and ones wrongly — 35 + 75 = 100 — shows partitioning is not secure. Fix the ones column first, then tens.
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Same facts, played
A short game that drills the same idea after the page is printed.