THE TRANSITION LINE // FIELD NOTES // STOP 04
Decimal places, rounding, and the circle
Field Book
Lessons 13 to 16
Method
Pencil and paper. Calculators never.
Room 1 opens this stop. Paper is the gate; the stamp is the pass. Place value crosses the decimal point, rounding fixes a target digit, lines and segments and rays get their names, averages come from a sum and a count, and the circle arrives with its three measurements.
What you have to be able to do
- Name decimal places and round to a target place
- Tell a segment, a ray, and a line apart
- Read mixed numbers off a number line
- Find an average
- Find diameter and circumference from a radius
The procedures
Decimal places and roundingField Book Lesson 13
- Tenths, hundredths, thousandths sit right of the point.
- To round: pick the target digit, keep everything to its left, zero everything to its right.
Segments, rays, lines, and points on the lineField Book Lesson 14
- A segment has two endpoints, a ray has one, a line has none.
- To read a marked point: whole number to the left, count the spaces for the bottom, count over for the top.
AverageField Book Lesson 15
- Add every value.
- Divide the sum by how many values were added.
The circleField Book Lesson 16
- Radius runs center to edge. Diameter runs edge to edge through the center, D = 2 · r.
- Circumference C = 2 · π · r. The Field Book works these with π taken as 3.
Worked: freight average
- Loads of 12, 19, 15, and 14 tons.
- Sum 60, divided by 4 loads, gives 15 tons.
Worked: around the wheel
- A wheel has radius 7 in, with π taken as 3.
- C = 2 · π · r = 2 · 3 · 7 = 42 in.
Terms on the record
| Term | Meaning |
|---|
| rounding | choosing which endpoint of an interval a number sits closer to |
| segment | a straight path with two endpoints |
| ray | a straight path with one endpoint, running on forever the other way |
| average | the sum of the values divided by the count of values |
| radius | the distance from the center of a circle to its edge |
| diameter | the distance edge to edge through the center, twice the radius |
| circumference | the perimeter of a circle |