## 2021 Oregon Math Guidance: 3.GM.C.7

**Cluster: 3.GM.C - Geometric measurement: understand concepts of area and relate area to multiplication and to addition. **

## STANDARD: 3.GM.C.7

### Standards Statement (2021):

Relate area to multiplication and addition. Use relevant representations to solve problems in authentic contexts.

### Connections:

Preceding Pathway Content (2021) | Subsequent Pathway Content (2021) | Cross Domain Connections (2021) | Common Core (CCSS) (2010) |

3.GM.C.6 | 4.GM.B.6, 5.NF.B.4 | 4.NBT.B.6 | 3.MD.C.7 3.GM.C Crosswalk |

### Standards Guidance:

#### Terminology

- The dimensions of a rectangle can be referred to as length and width OR base and height.
- A square with side length 1 unit, called “a unit square,” is said to have “one square unit” of area, and can be used to measure area (e.g., square cm, square m, square in, square ft).

#### Teaching Strategies

- Find the area of a rectangle with whole-number side lengths by tiling it, and show that the area is the same as would be found by multiplying the side lengths.
- Multiply side lengths to find areas of rectangles with whole number side lengths in the context of solving problems, and represent whole-number products as rectangular areas in mathematical reasoning.
- Use tiles and/or arrays to illustrate and explain that the area of a rectangle can be found by partitioning it into two smaller rectangles and that the area of the larger rectangle is the sum of the two smaller rectangles.
- Recognize area as additive. Find areas of rectilinear figures by decomposing them into non-overlapping rectangles and adding.

#### Progressions

- Students can be taught to multiply length measurements to find the area of a rectangular region. But, in order that they make sense of these quantities, they first learn to interpret measurement of rectangular regions as a multiplicative relationship of the number of square units in a row and the number of rows.
- Students learn to understand and explain that the area of a rectangular region of, for example, 12 length-units by 5 length-units can be found either by multiplying 12 x 5 or by adding two products, e.g., 10 x 5 and 2 x 5, illustrating the distributive property. (Please reference pages 17-18 in the Progression document)

#### Examples

- The area of a rectangle with whole-number side lengths a and b + c is the sum of a × b and a × c; 4 x 7 is the same as 4 x (2 + 5) and is the sum of 4 x 2 and 4 x 5.
- In a rectangular garden, you have four rows of peanut plants. There are 9 peanut plants in each row. How many peanut plants are there in the garden?
- Student Achievement Partners: