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math worksheets addition and subtraction up to 20

Practice focus: math worksheets addition and subtraction up to 20. Focus: Adding a One-Digit Number to 10. Use the worked example and teaching sequence below to explain the reasoning before independent practice.

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Teaching Notes

Practice focus: math worksheets addition and subtraction up to 20. Focus: Adding a One-Digit Number to 10. Use the worked example and teaching sequence below to explain the reasoning before independent practice.

Before You Begin

Teaching Steps for Parents and Teachers

  1. Read each number by place value.
  2. Add the ones, then the tens and any remaining places.
  3. When a column totals ten or more, exchange ten units for one unit in the next place.
  4. Record the carried amount before continuing.
  5. In a horizontal problem, you may rewrite the numbers vertically; the ones must still line up.
  6. Start in the ones place and subtract corresponding places.
  7. If a top digit is too small, exchange one unit from the next place for ten units in the current place.
  8. Mark both changes: the giving place decreases by one and the receiving place increases by ten.
  9. Continue left, using the changed digits.

Worked Examples

Evaluate 8+7.

  1. Place value 1: 8 + 7 = 15. Write 5 and carry 1 to the next place.
  2. Write the remaining 1 in the next place.

Answer: 15

Evaluate 17-9.

  1. Regroup from place value 10; it decreases by 1. There are now 17 units at place value 1.
  2. Place value 1: 17 − 9 = 8.
  3. Place value 10: 0 − 0 = 0.

Answer: 8

Common Mistakes and How to Help

A carried ten belongs in the next column. Do not write a two-digit total into a single place or forget to include a carry in the next sum.

Subtract one addend from the sum. The result should equal the other addend.

Do not reverse the digits just because the lower digit is larger. Subtraction keeps its original order. When a zero is involved, follow the exchange across the places rather than changing every zero independently.

Add the difference to the number subtracted. You should recover the starting number.

Questions to Check Understanding

Practice Advice

Work through the example together. Ask the learner to explain the first two problems, then try three independently. Review the first incorrect step before assigning more practice.

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