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Apply Mental Strategies to Add within 20

Students will use mental math strategies — such as making ten, using doubles, and counting on — to efficiently add two numbers within 20. The focus is on flexible thinking rather than counting by ones.

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Apply Mental Strategies to Add within 20

Grade 2 · Addition and Subtraction Fluency within 20 · question 1 of 3

0 of 12

12 rungs. A star at the top.

9 + 4 =

How it is taught

0:00 of 3:13

Doubles are a number plus itself.

A doubles fact can land you on 16.

Read it: Make 10 to add past 10

8 + 5: 8 needs 2 more to make 10. Take 2 from the 5, and 3 are left: 10 + 3 = 13.

  1. Start with the bigger number: 8.
  2. Move 2 over to make 10.
  3. Add what is left: 10 + 3 = 13.

10 is easy to add to: 10 and 3 is 13 without counting.

The 5 splits into 2 and 3, so no counters are lost or added.

So 8 + 5 is the same as 10 + 3, and both are 13.

Make 10 first, then add what is left.

Counting on 5 from 8 and losing count: 9, 10, 11, 12.

Make 10 with 2 of the 5. 3 are left: 13.

6 + 5 = ___ — 11. 6 and 4 make 10, and 1 more is 11.

8 + 5 (make ten)

Let's add eight plus five in our heads. Counting on our fingers takes a while — we can do better!

Here's a smart trick: let's make ten first. Tens are easy to add to.

Eight needs two more to reach ten. So let's split the five into two and three.

8 + 5 = ?8+5=?Make ten!8+52301581013start+210!We made ten!+313ANSWER138 + 5
Grade 2 · Use the make-ten strategy to add

Five equals two plus three. Now we have a plan.

Start at eight on the number line.

Jump up two… and we land right on ten!

Ten is a friendly number. We have three more to add.

Jump three more: ten, eleven, twelve, thirteen.

Eight plus five is thirteen. Make ten — it works every time!

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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