Grade Level: 4th Skill: Graphs and Charts Topic: X-Coordinates Goal: Understand that the length of a horizontal line segment equals the difference of the x-coordinates. Skill Description: Use subtraction to find the horizontal length of the line on a coordinate grid.

## Building Blocks/Prerequisites

### Sample Problems

 (1) Graph the ordered pairs and connect the points. Find the length of the line segment. (2,6) and (15,6) (15 -2 = 13) (2) What is the length of the line segment with points (9, 8) and (18, 8) (18 – 9 = 9) (3) Use the coordinate grid and find the length of the line segment. [Graph the coordinates below on a coordinate grid] (4,5) and (7,5) (4) Which ordered pairs has the horizontal distance of 19 units: (21,6) (2,6) (6,21) (6,3) (6,3) (21,6) (a) (5) If Jay plots a point at (9, 3) where should he plot his second point to have a horizontal length of 4 units? (13,3 or 5,3)

### Learning Tips

 (1) Math Vocabulary: Ordered pair- (x, y) a pair of numbers used to locate a point on a coordinate grid. x-axis- the horizontal line on a coordinate grid (line that goes from left to right) y-axis- the vertical line on a coordinate grid (line that goes from top to bottom) x-coordinate- the first number of an ordered pair, which tells how far to move horizontally along the x-axis. y-coordinate- the second number in an ordered pair, which tells how far to move vertically along the y-axis Horizontal line- a line that goes across from left to right or right to left i.e.) ---------------- Line segment- a line that has two endpoints i.e.) •---------------------• Coordinate grid- a map-like tool that is used to locate specific points. (2) Use a number line to explain length of the x-axis: ‹--׀--------•--------׀--------׀--------׀--------•--------׀--------׀--------׀--------׀---› 1 2 3 4 5 6 7 8 9 10 → → → → The length is 4 units (count the arrows from one number to the next). There are 4 units between 2 and 6. To find the horizontal distance between two points on a coordinate grid, count units or subtract the x-coordinates (6 – 2 =4 units). (3) Color-code the x-axis. Most children get confused on finding the length of the horizontal and vertical distance because they subtract the wrong coordinates. In the beginning color-code the x-coordinates, so they understand that those are the two numbers that are to be subtracted (Hint: the y-coordinate should be the same number) Use a red marker to outline the x-coordinate. For example, What is the horizontal length of (2, 3) and (4, 3)? If they see the x-coordinates color coded it will help them grasp the concept of subtracting the x-coordinates to find the length. (4) Relate coordinate grids to Maps: Use a real map and teach your child how to use the coordinate grid on a map to find cities in the US. On most maps, the coordinates are letters and numbers. To find a location they will be given a coordinate of C-2 and the city will be labeled at that point. Once they understand how to use coordinates to locate locations, have them find the horizontal distance between two cities. (5) Explain the parts of a coordinate grid: Draw a coordinate grid on large chart paper and identify the parts of the grid y-axis x-axis how to plot points (x-coordinate go across on the x-axis; y-coordinate go straight up from the x-coordinate to number on the y-axis) horizontal lines vertical lines Practice making horizontal lines. Parent will give the child two ordered pairs have the child graph and connect the points. Discuss why it is a horizontal line and not vertical. (6) Practice simple subtractions facts (timed drills, flash cards)

### Extra Help Problems

 (1) Graph the ordered pairs and connect the points. Find the length of the line segment. (5, 7) and (18, 7) (13) (2) Graph the ordered pairs and connect the points. Find the length of the line segment. (16,3) and (19,3) (3) (3) Graph the ordered pairs and connect the points. Find the length of the line segment. (4,12) and (16,12) (12) (4) Graph the ordered pairs and connect the points. Find the length of the line segment. (9,9) and (18,9) (9) (5) Graph the ordered pairs and connect the points. Find the length of the line segment. (0,1) and (10,1) (10) (6) Graph the ordered pairs and connect the points. Find the length of the line segment. (15,0) and (8, 0) (7) (7) What is the length of the line segment with points (117, 10) and (93, 10)? (24) (8) What is the length of the line segment with points (57, 12) and (29, 12)? (28) (9) What is the length of the line segment with points (15, 15) and (9, 15)? (6) (10) What is the length of the line segment with points (66, 7) and (7, 7)? (59) (11) What is the length of the line segment with points (34, 66) and (33, 66)? (1) (12) What is the length of the line segment with points (12, 15) and (12, 15)? (0) (13) Use the coordinate grid and find the length of the line segment. (Do not show ordered pairs, only the graph) [Graph (4,6) and (8,6)] (14) Use the coordinate grid and find the length of the line segment. . (Do not show ordered pairs, only the graph) [Graph (11,1) and (3, 1)] (15) Use the coordinate grid and find the length of the line segment. . (Do not show ordered pairs, only the graph) [Graph (3,2) and (15, 2)] (16) Use the coordinate grid and find the length of the line segment. . (Do not show ordered pairs, only the graph) [Graph (1, 10) and (6, 10)] (17) Use the coordinate grid and find the length of the line segment. . (Do not show ordered pairs, only the graph) [Graph (7,8) and (9,8)] (18) Which ordered pairs has the horizontal distance of 37 units (13,8) and (45, 13) (8,13) and (45, 13) (21, 8) and (37, 8) (b) (19) Which ordered pairs has the horizontal distance of 2 units (6, 6) and (6, 4) (12,6) and (9, 6) (6, 6) and (4, 6) (c) (20) Which ordered pairs has the horizontal distance of 72 units (111,40) and (39, 40) (8, 40) and (9, 40) (40, 111) and (40, 39) (a) (21) Which ordered pairs has the horizontal distance of 23 units (46, 18) and (2, 18) (23, 18) and (46, 18) (23, 18) and (18, 46) (b) (22) Which ordered pairs has the horizontal distance of 14 units (22, 20) and (14, 20) (20, 22) and (14, 22) (8, 20) and (22, 20) (c) (23) If Allison plots a point at (17, 20) where should she plot her second point to have a horizontal length of 12 units? (29,20 or 5,20) (24) If Craig plots a point at (3, 9) where should he plot his second point to have a horizontal length of 21 units? (24,9) (25) If Sarah needed a horizontal length of 12 units and she plotted her points at (8, 24) and (8, 12), what mistake did she make? (She made a vertical length of 12 units not, horizontal)