Subtraction

Ages 59

Difficulty adapts to you

Subtraction

Subtraction means taking away from a group to find what remains. The symbol is − (minus). The answer is called the difference.

Your goals

  • You can take away to find what is left.
  • You can use difference, exchange correctly.
  • You can add your answer to the number that was subtracted.

Words to know

difference:
The result of subtraction, or the distance between two values.
exchange:
Regroup one place-value unit as smaller units.

Examples

  • 19 − 4 = 5 — nine take away four leaves five.
  • 215 − 7 = 8 — fifteen take away seven leaves eight.

More than one way to solve it

Try each method, then choose the one you can explain and check most clearly.

Method 1

Count up to find the difference

Best for: Numbers that are close together
  1. 1.Start at the smaller number.
  2. 2.Jump to friendly landmarks.
  3. 3.Add the jumps.

Example: 82 - 67: 67→70 is 3, 70→80 is 10, 80→82 is 2; total 15.

Method 2

Partition and exchange

Best for: Written subtraction
  1. 1.Align place values.
  2. 2.Exchange from the next column when needed.
  3. 3.Subtract each column.

Example: 403 - 178 uses one hundred exchanged into tens, then one ten into ones.

Check these

  • Do not subtract the smaller digit from the larger digit without considering place value.
  • Keep every number, symbol, label, and unit in its correct place.
  • Choose the method that makes each step easiest to explain and check.

Helpful habits

  • Read the whole question before choosing what to do.
  • Show one clear step at a time and check each step.
  • If you are stuck, draw a model, try smaller numbers, or revisit the example.

Now try your own

Create your own subtraction example, solve it, and explain how you checked it.

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