Split strategy: break numbers into tens and ones. For 47 + 36, add the tens (70), add the ones (13), then combine: 83. For subtraction, take away the tens and then the ones. Compensation: when a number is close to a round number, use the round number and then fix it. For 46 + 29, add 30 to get 76, then take away the extra 1: 75.
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
- partition
- split a number into parts, such as tens and ones
- compensate
- use a friendlier number, then adjust the answer to make up for it
Worked examples
47 + 36 = ?
- 1.Tens: 40 + 30 = 70. Ones: 7 + 6 = 13.
- 2.70 + 13 = 83.
= 83
73 − 38 = ?
- 1.38 is close to 40. 73 − 40 = 33.
- 2.40 is 2 more than 38, so give 2 back: 33 + 2 = 35.
= 35
364 + 198 = ?
- 1.198 is 2 less than 200. 364 + 200 = 564.
- 2.You added 2 too many: 564 − 2 = 562.
= 562
For parents
Method: Split strategy and compensation
What to say: Which number is close to a ten or a hundred? Did you add too much or too little? How will you fix it?
Common mistakes:
- Adds the tens and the ones separately but loses the new ten made by the ones.
- Writes the tens total and the ones total next to each other instead of adding them.
- When taking away the ones, takes the smaller ones digit from the larger instead of bridging back through a ten.
- Adds or subtracts the tens of the second number and forgets its ones.
- Uses the round number in place of the real number and forgets to adjust afterwards.
- Adjusts the compensation in the wrong direction.