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Subtraction Shortcuts

Round and adjust for fast subtraction.

When to use

Subtracting when one number is close to a round number.

Steps

  1. 1.Round the number being subtracted to the nearest 10
  2. 2.Subtract the rounded number
  3. 3.Adjust for the rounding

Example: 607 - 58

Round 58 up to 60 (subtracting 2 too many)

607 - 60 = 547

Add back the extra 2: 547 + 2 = 549

Mental approach

607 - 58: think 607 - 60 = 547 then add back 2 = 549.

Pen & paper approach

Standard column subtraction or complementary addition.

Tips

  • •Round the subtracted number UP, then add the difference back
  • •For 244 - 88: think 244 - 90 + 2 = 156
  • •Check: does the answer make sense? Quick ballpark: 600 - 60 = 540 ✓

Try it yourself

755 - 32

412 - 97

1,003 - 46