98
The number ray
Textbook: Part 3, lesson 98, pp. 92–94
GoalThe number ray: starting point, direction, unit segment; the coordinate of a point; the value of a division.
New words
number ray · koordinata nuriorigin (zero) · sanoq boshiunit segment · birlik kesmacoordinate · koordinata
Explanation
A number ray is a ray with a starting point (0), an arrow showing the direction in which numbers grow, and equal segments marked on it. It looks like a ruler. The number under a point tells how far the point is from zero; it is the coordinate of the point. If the coordinate of A is 5 we write A(5). Sometimes each step on the ray is not 1 but, say, 4: 0, 4, 8, 12 … This is the value of a division.
Worked examples
On a ray where the unit is 2 squares, point M(7) is 7 × 2 = 14 squares from zero.
A ray shows 0, 6, 12, … The value of a division is 6. The mark after 12 is 12 + 6 = 18, and the next is 24.
Class activity
“Human number ray”: a track from 0 to 10 is marked on the floor. Children stand at the number on their card (for example K(6)). Then we play again with each step equal to 2 units.
Practice
1
Points A(3) and B(9) are marked on a ray. How many unit segments are between them?
6
2
On a ray whose division value is 4, which number is at the 5th mark to the right of zero?
20
3
A ray shows 0, 6, 12, …, 24. What is the number between 12 and 24?
18
4
Find the coordinate of the point P(48 : 8).
6
5
On a ray with a unit of 2 squares, how many squares is M(7) from zero?
14