Grade 1Tens and Ones1.NBT.C.6

Subtracting Tens

Subtract multiples of 10, like 70 − 30.

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You can count by tens backward, too. That helps you subtract tens.

Press “Take away 30.” Three ten-sticks go away, and 4 are left.

Key idea

$70 - 30$ is 7 tens take away 3 tens, which leaves 4 tens: 40.

Why it works

Tens work just like ones. $7 - 3 = 4$, so 7 tens − 3 tens = 4 tens.

Worked example: Take away tens

What is $90 - 40$?
  1. 9 tens − 4 tens.
  2. $9 - 4 = 5$, so 5 tens.
  3. $90 - 40 = 50$

Answer: 50

Worked example: Boxes of crayons

There are 5 boxes of 10 crayons. Ana gives away 2 boxes. How many crayons are left?
  1. 5 boxes of 10 is 50. 2 boxes is 20.
  2. 5 tens − 2 tens = 3 tens.
  3. $50 - 20 = 30$ crayons.

Answer: 30 crayons

For grown-ups: Use bundles of 10 straws: start with 8 bundles, take some away, and count what is left by tens.

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

This is one of the top rungs of Grade 1.

Sources and further reading

  • Common Core State Standards for Mathematics, Grade 1, 1.NBT.C.6: subtract multiples of 10 in the range 10 to 90
  • Institute of Education Sciences practice guide: Assisting Students Struggling with Mathematics: Intervention in the Elementary Grades (WWC 2021006)
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