Fishtank Learning

3rd Grade Math
Unit 4: Area
Lesson 5

Objective

Find the area of a rectangle that has been superimposed over a grid.

Anchor Tasks - Problem 1

Label the following shaded rectangle with the number of rows and columns of unit squares that it consists of. Then find its area.

Shaded rectangle with 3 rows and 5 columns; area is 15 square units.

Guiding Questions

How many rows of unit squares are there? How many columns? How do you know?
Why don’t we need to draw the rows and columns to show individual square units in the rectangle in order to find its area?
What is the area of this rectangle? How do you know?

Notes

Students might still want to draw a grid inside of the rectangle in order to find its area, which is fine. Encourage them to draw rows and columns, though, instead of individual units.
You may decide not to ask the last questions, based on students’ spatial structuring. If students are still dependent on seeing individual units in order to find the area, then I would skip the question, but if they are growing increasingly reliant on skip-counting or multiplication, then ask.

Anchor Tasks - Problem 2

Label the following shaded rectangle with the number of rows and columns of unit squares that it consists of. Then find its area.

Shaded rectangle with 4 rows and 5 columns; area is 20 square units.

Guiding Questions

How many rows of unit squares are there? How many columns? How do you know?
Why don’t we need to draw the rows and columns to show individual square units in the rectangle in order to find its area?
What is the area of this rectangle? How do you know?

Notes

This Anchor Task is optional, though it may help build students’ multiplicative strategies to find the area since the length, width, and area are all greater than those in Anchor Task 1.

Problem Set

View Problem Set

Discussion of Problem Set

Which two figures have the same area in #1? What are the number of rows and columns of unit squares of each of those figures? What do you notice about their rows and columns as compared to their area?
How can Mila and Jorge both be right in #4? What could the area of the rectangle possibly be? Is there more than one possibility?

Target Task

Label the number of rows and columns of unit squares of the rectangle below. Then find the total area of the rectangle.

Rectangle with 6 rows and 10 columns; total area is 60 square units.

Word Problem

Alice has 18 Uno cards. She draws 14 more cards on her next turn. Now, she has an equal number of cards of each color. How many of each color does she have?