THE TRANSITION LINE // FIELD NOTES // STOP 02
Missing factors, first fractions, and perimeter
Method
Pencil and paper. Calculators never.
The freight rule holds: know the largest, or find it. The missing-number rule grows to multiplication and division and to story problems, fractions make their first appearance, and perimeter walks the outside of a shape.
What you have to be able to do
- Find a missing number in a multiplication or division statement
- Set up missing-number story problems
- Read a fraction and take a unit fraction of a number
- Find the perimeter of a rectangle
The procedures
Missing numbers: multiply and divideField Book Lesson 5
- Decide whether the missing number sits in the largest position.
- Missing the largest number: multiply the two given numbers. Otherwise: divide.
Missing numbers in storiesField Book Lesson 6
- Name the total in the story.
- Missing the total: add the parts. Given the total: subtract the known part.
What a fraction saysField Book Lesson 7
- The bottom counts the equal parts of the whole. The top counts the parts selected.
- For a unit fraction of a number, divide the number by the bottom.
Perimeter of a rectangleField Book Lesson 8
- Perimeter is the distance around the outside of a closed, flat shape.
- Add every outside edge exactly once.
Worked: one fifth of the shipment
- 15 of 90 crates: divide by the bottom.
- 90 รท 5 = 18, so 18 crates.
Worked: around the platform
- A platform runs 26 ft by 9 ft.
- P = 26 + 9 + 26 + 9 = 70 ft.
Terms on the record
| Term | Meaning |
|---|
| fraction | a count of selected parts over a count of equal parts of a whole |
| numerator | the top number: how many parts are selected |
| denominator | the bottom number: how many equal parts the whole is cut into |
| perimeter | the distance around the outside of a closed, flat shape |