3.4A Add/Subtract Whole Numbers

Objective:
I can represent, solve, and generate two-step addition and
subtraction word problems.

Guiding Question: What does the context of the problem
tell me about what is known and what I need to find out?

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Let’s Explore

Use base-ten blocks and place value mats to solve:

93 - 37

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Tens

Ones

Here is one way to solve:

Decompose 93 90 + 3

Decompose 90 as 80 + 10

Regroup a group
of ten to make
10 ones.

93 is the same as 8 groups of ten and 13 ones

Base Ten Models Created by HISD Curriculum using 1, 2, 3 Math Fonts under license.

Fill in the Blank

93 - 37

Let’s Explore

Use base-ten blocks and place value mats to solve:

93 - 37

Created by HISD Curriculum using Google® Slides

Tens

Ones

Remove 37 Decompose 37 as 30 + 7

Remove 30

Remove 7

The difference is 56.

Base Ten Models Created by HISD Curriculum using 1, 2, 3 Math Fonts under license.

Let’s Review

Read the following math story.

Blake had 27 seashells. Then, she went to the beach and picked up
6 more seashells. When Blake returned home, she gave 19 of these
seashells to her brother. How many seashells does Blake have now?

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What is the problem about?

What are we trying to figure out?

What information is known? What
information is unknown?

Let’s Review

I can use base ten blocks to represent what is happening in the math story.

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Step 1

Result

At the beginning of the story,
Blake had 27 seashells.

Then, something changed.
Blake went to the beach and
picked up 6 more seashells.

We can combine the seashells.

Regroup
10 units
to make
1 long.

These are the shells Blake had after she
went to the beach.

Blake had 27 seashells. Then, she went to the beach and
picked up 6 more seashells.When Blake returned home,
she gave 19 of these seashells to her brother. How many
seashells does Blake have now?

Base Ten Models Created by HISD Curriculum using 1, 2, 3 Math Fonts under license.

Base Ten Models Created by HISD Curriculum using 1, 2, 3 Math Fonts under license.

Let’s Review

I can use base ten blocks to represent what is happening in the math story.

Created by HISD Curriculum using Google® Slides

Step 2

Result

I can represent this problem with
the equation 27+ 6 – 19 = 14

I need to subtract 19
from 33, but I have
to decompose a ten
to have enough ones
to subtract 9 ones.

Blake had 27 seashells. Then, she went to the beach and picked up 6 more
seashells. When Blake returned home, she gave 19 of these seashells to
her brother. How many seashells does Blake have now?

These are the shells Blake had after she went
to the beach.

Now, I can
subtract 19.

Blake has 14 seashells now.

33 - 19 = 14

The result is 14.

Base Ten Models Created by HISD Curriculum using 1, 2, 3 Math Fonts under license.

Base Ten Models Created by HISD Curriculum using 1, 2, 3 Math Fonts under license.

Let’s Practice

Let’s practice representing and solving the following problem:

Riley had 37 seashells. Then, she went to the beach and picked up
16 more seashells. When Riley returned home, she gave 19 of these
seashells to her brother. How many seashells does Riley have now?

Created by HISD Curriculum using Google® Slides

Represent the problem with an equation and solve using base-ten blocks.

Fill in the Blank

Riley had 37 seashells. Then, she went to the beach and picked up 16 more seashells. When Riley returned home, she gave 19 of these seashells to her brother. How many seashells does Riley have now?

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