Addition Shortcuts: Make 9s and 19s Easy

The fastest mental math comes from turning awkward numbers into friendly ones.

For additions like 9 or 19, use the +10 trick: add 10, then subtract 1. Example: 47 + 9 → 47 + 10 − 1 = 56.

For 19, do the same: 63 + 19 → 63 + 20 − 1 = 82. This keeps your brain in “tens mode”.

Practice: whenever you see 9, 19, 29, treat it as “next ten minus one”.

• 9 = 10 − 1 (always)
• 19 = 20 − 1 (always)
• If you hesitate, slow down for one task, then resume

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