Students use the count-on method or the relationship between addition and subtraction to find the missing number if it is an addend. Also, they add the addends to get the sum if the missing number is the sum. There is a lot of practice with this concept in the worksheet add two multiples of 10. As the worksheet uses a horizontal format, it allows for more creativity when it comes to how the student solves the problem. In contrast, in the vertical format, students usually employ the standard method to solve.
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