Key Concepts and Glossary

Key Concepts

Add Whole Numbers

• Addition Notation To describe addition, we can use symbols and words.

  Operation	Notation	Expression	Read as	Result
  Addition	\(+\)	\(3 + 4\)	three plus four	the sum of \(3\) and \(4\)

• Identity Property of Addition
  • The sum of any number \(a\) and \(0\) is the number. \(a + 0 = a\) \(0 + a = a\)
• Commutative Property of Addition
  • Changing the order of the addends \(a\) and \(b\) does not change their sum. \(a + b = b + a.\)
• Add whole numbers.
  1. Write the numbers so each place value lines up vertically.
  2. Add the digits in each place value. Work from right to left starting with the ones place. If a sum in a place value is more than 9, carry to the next place value.
  3. Continue adding each place value from right to left, adding each place value and carrying if needed.

Subtract Whole Numbers

• Subtract whole numbers.
  1. Write the numbers so each place value lines up vertically.
  2. Subtract the digits in each place value. Work from right to left starting with the ones place. If the digit on top is less than the digit below, borrow as needed.
  3. Continue subtracting each place value from right to left, borrowing if needed.
  4. Check by adding.

Glossary

sum

The sum is the result of adding two or more numbers.

difference

The difference is the result of subtracting two or more numbers.