Subtraction: fill in the missing digits

Key notes:

🔹 Introduction
  • Subtraction means taking away one number from another.
  • Sometimes in subtraction problems, one or more digits are missing.
  • We use our knowledge of subtraction to find the missing digit.
🔹 Steps to Solve
  • Look at the subtraction column by column (from right to left).
  • Check if borrowing (regrouping) is needed.
  • Compare the given digits to identify what number is missing.
  • Fill in the missing digit so that subtraction is correct.
  • Verify by adding the difference and the subtrahend – it should equal the minuend.
🔹 Examples

Example 1

  5 7 2
- 3  ?  1
-------
  2 3 1
  • 👉 Look at the tens place:
  • ? must be 4, because 7 – 4 = 3.
  • Answer: Missing digit = 4

Example 2

  6 ? 8
-  4 5 2
--------
   1 6 6
  • 👉 Look at the hundreds place:
  • ? must be 2, because 628 – 452 = 176.
  • Answer: Missing digit = 2

Example 3 (with borrowing)

  4 ? 2
- 2 7 5
--------
  1 6 7
  • 👉 Look at the tens place:
  • Borrowing needed. ? must be 3, because after borrowing 12 – 5 = 7.
  • Answer: Missing digit = 3
🔹 Key Points to Remember
  • Always subtract ones → tens → hundreds → thousands.
  • If subtraction is not possible, borrow from the next digit.
  • Use addition to check your answer.
  • Be careful with borrowing when filling missing digits.
🔹 Practice Problems

Fill in the missing digits:

1.

  7 ? 4
- 4 2 1
--------
  3 1 3

2.

  ? 6 8
-  2 9 4
--------
   3 7 4

3.

  8 5 ?
-  3 7 8
--------
   4 7 4

4.

  9 ? 2
-  4 6 8
--------
   5 2 4

Learn with an example

🎯 Type the missing digit:

Start on the right. Subtract the ones and tens columns, remembering to carry over. Look at the hundreds column. You want to find a number that, when 8 is subtracted from it, gives a difference of 1. 9 − 8 = 1. The missing number is 9.

🎯 Type the missing digit:

Start on the right. Look at the ones column. You want to find a number that, when 3 is subtracted from it, gives a difference of 5. 8 − 3 = 5. The missing number is 8.

🔥Type the missing digit:

Start on the right. Subtract the ones and tens columns, remembering to carry over. Look at the hundreds column. You want to find a number that, when subtracted from 9, gives a difference of 7. 9 − 2 = 7. The missing number is 2.

Let’s practice!