Grade 1Adding and Subtracting within 201.OA.C.5

Counting Back to Subtract

Start at the total and count back.

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Counting on adds. Counting back subtracts.

$12 - 3$: start at 12 and hop back 3: 11, 10, 9.

Key idea

To take away a small number, start at the total and count back.

Why it works

Each step back takes one away. Three steps back take three away.

Worked example: Count back 3

What is $9 - 3$?
  1. Start at 9.
  2. Count back 3: 8, 7, 6.
  3. $9 - 3 = 6$

Answer: 6

Common mistake

Saying the starting number as the first step back: “9, 8, 7” gives 7 for $9 - 3$. The first step back lands on 8.
For grown-ups: Count back together while walking down stairs. Say the step you land on, not the one you stand on.

Practice

Pass with 3 right answers, the last 2 in a row. Each right answer earns 1 XP.

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Builds on

Leads to

Sources and further reading

  • Common Core State Standards for Mathematics, Grade 1, 1.OA.C.5: relate counting to addition and subtraction, such as counting back
  • Institute of Education Sciences practice guide: Assisting Students Struggling with Mathematics: Intervention in the Elementary Grades (WWC 2021006)
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