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Subtract within 20 by Bridging 10

Students subtract within 20 when crossing 10 is required (e.g., 13 − 5). They use make-a-ten backwards or think-addition to bridge the ten.

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Subtract within 20 by Bridging 10

Grade 1 · Counting, Fluency, and Fact Strategies · question 1 of 3

0 of 12

12 rungs. A star at the top.

11 − 3 =

How it is taught

0:00 of 2:36

Bridge 10 means subtract to 10 first.

Then take away what is still left.

Read it: Back through 10

14 − 6. 14 is 10 and 4. Take the 4 first to get to 10, then 2 more: 8. So 14 − 6 = 8.

  1. Split the 6 into 4 and 2.
  2. Take 4: back to 10.
  3. Take 2 more from the 10: 8.

The 4 ones are not enough to take 6, so go back to 10 first.

10 is easy to take from: 10 − 2 = 8.

It is make 10, backwards: 14, then 10, then 8.

Take the ones to get back to 10. Then take the rest from the 10.

Taking 4 from 6 instead, because 6 − 4 is easy, and writing 12.

There are only 4 ones. Take them, then 2 more from the 10: 8.

13 − 7 = ___ — 6. Take 3 to get to 10, then 4 more: 6.

13 − 5

Imagine thirteen cupcakes on a tray. We eat five of them. How many are left?

Let's count back on a number line. We start at thirteen.

Five is a big jump. We'll stop at ten on the way — that makes it easier.

We can break five into three and two. Three to get to ten, then two more.

From thirteen, how many hops back land us on ten?

Three! Hop back three. Now we're standing on ten.

We've used three of our five. Two more to subtract.

Hop back two more from ten.

13 cupcakes, eat 5 — how many left?13 − 5 = ?13 − 5 = 8Stop at 10 on the way!058101315135= 3 + 2−310Used 3 · still need to take away 2−28ANSWER8cupcakes left
Grade 1 · Make a ten the smart way back

We land on eight. Thirteen minus five is eight. Nice bridging!

What you see

While they climb, your page writes one true line to ask about tonight, and a short note each Sunday.

MayaGrade 3 · Mathematics
Did you know?

A chessboard has 64 squares — share them out between the 8 rows and each row holds exactly 8.

Today’s goal
1 star — one skill mastered, every rung of its ladder climbed
Climbing now
Divide within 100

An example student.

MayaGrade 3 · Mathematics

Maya earned 2 stars this week — Interpret multiplication as equal groups, which took 6 answers over 3 days before its star landed 3 days ago and Multiply by 6, 7, 8 and 9. Next up: Divide within 100.

An example week.

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