100
Number Bonds to 100
Bonds to one hundred: tens sums, the jump to the next ten, pairs that make one hundred, and clever shortcuts.
Choose what to practise
Each round is 10 questions, and takes 5 to 10 minutes.
Finished
Bonds to one hundred: tens sums, the jump to the next ten, pairs that make one hundred, and clever shortcuts.
Choose what to practise
Each round is 10 questions, and takes 5 to 10 minutes.
Finished
In Year 2, children become fluent with addition and subtraction facts to 20, and use them to work out related facts up to 100. From there, they find pairs of two-digit numbers that make 100, such as 37 + 63.
Say it in tens. Because 3 and 7 make 10, 3 tens and 7 tens make 10 tens, or 100. Subtraction works the same way. Taking 3 tens from 9 tens leaves 6 tens, so 90 − 30 = 60.
Make the next ten, then count the tens. To find the number that goes with 37 to make 100, count on 3 to reach 40, then 60 more to reach 100. The jumps are 3 and 60, so the answer is 63.
Adding 19 is adding 20, then taking 1 away. So 46 + 19 is 46 + 20 − 1 = 65. In the same way, 46 + 21 is 46 + 20 + 1 = 67.
Watch out for swapping the digits. Asked what goes with 37 to make 100, some children say 73, perhaps because 3 and 7 make 10. Add the two numbers to check, and 37 + 73 comes to 110. The ones, 7 and 3, make 10 on their own. To reach 100 altogether, the tens must make the other 90. Since 30 + 60 = 90, the answer is 63.
If facts to 20 are not yet automatic, practise the Year 1 game Number Bonds to 20 first.
In Year 3, children add and subtract ones, tens or hundreds to and from a three-digit number in their heads, and learn column methods for numbers with up to 3 digits. Bonds to 100 also give change from £1. If something costs 37p, the change is 63p, because 37 + 63 = 100.
The next game on the Addition and Subtraction path is Addition within 100.