Addition: fill in the missing digits

Key notes :

๐ŸŽˆ1. Understanding the Concept

  • Missing Digits: In addition problems where some digits are missing, the goal is to find the missing numbers to complete the equation.
  • Purpose: Helps students understand place value, addition, and the structure of numbers.

๐ŸŽ†2. Steps to Solve Problems with Missing Digits

  1. Analyze the Problem:
    • Identify where the missing digits are located and understand their place value.
    • Example: _53+2_7=800
  2. Use Place Value:
    • Understand that each place (units, tens, hundreds) must be correctly filled to make the addition accurate.
    • Example: If the sum is 800, you need to ensure that the digits you fill in result in 800 when added.
  3. Work from Right to Left:
    • Start with the rightmost column and use the known digits to find the missing ones.
    • Example: If the units column is _+7=0 (or 10), you need to find that the missing digit is 3 (since 7 + 3 = 10).
  4. Carry Over if Needed:
    • If the sum of a column is 10 or more, carry over the tens to the next column.
    • Example: In 5_+_7=800 if the sum of the units column is 10 or more, ensure to carry over.
  5. Complete the Equation:
    • Fill in the missing digits ensuring the entire addition problem makes sense and satisfies the equation.
    • Example: After determining the missing digits, verify the sum of each column and the overall result.

๐ŸŽ‡3. Example Problems

  1. Example 1:
  1. Example 2:

Example 3:

๐Ÿงจ4. Tips for Solving

  • Use Place Value: Pay attention to each column and how digits interact within that column.
  • Check Carry Over: Ensure that any carry from one column is added to the next column correctly.
  • Verify the Solution: After finding the missing digits, check your work by adding the numbers to see if they match the given total.

Learn with an example

  • Start on the right. Add the ones column, remembering to carry over. Look at the tens column. The tens column must add up to 0 or 10. The missing number is 2. Remember to carry over.
  • Start on the right. Look at the ones column. Add the ones. The missing number is 8.
  • Start on the right. Add the ones and tens columns, remembering to carry over. Look at the hundreds column. The hundreds column must add up to 2 or 12. The missing number is 4. Remember to carry over.

Let’s practice!