First Grade · Math · week 7

Subtract by counting back

Subtract within 20 by counting back from the larger number.

To subtract a small number, start at the bigger number and count BACKWARD one hop for each number you are taking away. For 9 - 3, start at 9 and hop back three times: 8, 7, 6. So 9 - 3 = 6.

Counting back works best when you subtract a small number, like 1, 2, or 3. For bigger numbers, another strategy is faster -- you will learn it next week.

📋 For the teacher
Teach it (10–15 min):
  • Hop backward on a number line or hundred chart so the direction is visible.
  • Keep this strategy for subtracting 1, 2, or 3 only -- bigger numbers get a better tool soon.
  • Count out loud together, landing hard on each number, so no hop gets skipped.
  • Use fingers going down (10, 9, 8...) if a number line is not handy.
Talk about it:
  • Which number do you start on when you count back?
  • Why is counting back good for small numbers but not huge ones?
  • How many hops back for 12 - 3?

Mastery looks like: They count back accurately to subtract 1, 2, or 3 from any number within 20.

Common stumbles: Starting the count on the wrong number; losing track after more than three hops.

See it visually

Interactive, spoken-aloud tools that show this idea in motion.

SubtractionTake away and count back, step by step.try →Counting & Ten-FramesCount objects in ten-frames and base-ten blocks, one tap at a time.try →
Homework for this lessonType it, write it with a stylus, or print it for pencil & paper.open →
Records attendance + 15 min of Math for this learner.
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