To add or subtract, split the second number into tens and ones and jump along a number line. Jump the tens first, then the ones. When the ones cross a ten, jump to the ten first and then jump the rest. A number sentence can have a missing part: the whole is the biggest number, so take the known part away from it to find the missing part. For a story with two steps, do one step at a time and write a number sentence for each.
Explore this idea with maths tools
Maths you can move
Build 8 + 5
Tap two gold counters to fill the ten-frame.
8 in the frame + 5 waiting. The total stays the same.
Words to know
- split
- break a number into tens and ones
- jump strategy
- moving along a number line in jumps
- part-part-whole
- two parts that make a whole
Worked examples
47 + 26
- 1.Split 26 into 20 and 6.
- 2.Jump 20: 47 + 20 = 67.
- 3.Jump 6 through the ten: 67 + 3 = 70, then 70 + 3 = 73.
= 73
62 − 27
- 1.Split 27 into 20 and 7.
- 2.Jump back 20: 62 − 20 = 42.
- 3.Jump back 7 through the ten: 42 − 2 = 40, then 40 − 5 = 35.
= 35
What number makes this true? ___ + 28 = 63
- 1.The whole is 63. One part is 28.
- 2.Take the part from the whole: 63 − 28.
- 3.63 − 20 = 43, then 43 − 8 = 35. Check: 35 + 28 = 63.
= 35
For parents
Method: Split the second number, then jump the tens and the ones on a number line.
What to say: Is the answer bigger or smaller than the start? How many tens are you jumping? Did the ones cross a ten?
Common mistakes:
- Does not rename ten ones as a ten, so the answer is one ten too small.
- Subtracts the smaller digit from the larger in each place, whichever number it belongs to.
- Adds when the sentence is a subtraction, or subtracts when it is an addition.
- Splits the second number but only uses its tens, forgetting to deal with its ones.
- Adds the two numbers in a missing-part sentence instead of finding the difference.
- Does only the first step of a two-step story.
- Adds every number in the story, even the one that is given away.
- Jumps one ten too many.
- Is one out when bridging through ten.