“Plotting Points on a Coordinate Plane” – the topic sounds dry and boring, but it’s typically one of students’ favorites. At least, that’s what I found to be true in my upper-elementary and middle-school math classes. Remember the game “Battleship”? Moving on a coordinate plane is sort of like putting that game to pencil and paper. Kids have fun learning this skill because they can create cool pictures and play interactive games, but the best part is they’re becoming efficient map and grid readers.
Basics
Students need to understand this basic terminology. Use an overhead projection to demonstrate each.
- A coordinate plane is formed by the intersection of two number lines, one vertical and one horizontal.
- The vertical line is called the y-axis. Hint: Think of the vertical line on the bottom of the letter Y.
- The horizontal line is called the x-axis.
- The spot where the two number lines intersect or meet is called the origin.
- Always begin plotting points at the origin.
- The two intersecting lines divide the plane into four sections called quadrants.
- An ordered pair is a way to name any point on the grid. It’s simply a pair of numbers in a certain order.
Ordered Pairs
In an ordered pair, the first number is the x-coordinate and the second number is the y-coordinate, (x,y). Hint: x comes before y in the alphabet too. The numbers can be positive, negative or zero. When they’re both zero, (0,0), that point is the origin. They can be different numbers or the same number.
Examples: (3, 4.5); (-5, 2); (7, 0); (-25, -1); (11, -4); (8, 8)
Plotting Points
To plot a point, start at the origin. Alert: Start counting when you move off the origin.
Plot x, then y. Some people think of “HumVee” to help them remember to plot the Horizontal and then the Vertical coordinate. (I heard a lot of “HumVee” buzzing in my class!)
X: Move horizontally, right or left. If the first number in the ordered pair is positive, move to the right. If it’s negative, move to the left.
Y: Move vertically, up or down. If the second number in the ordered pair is positive, go up. If it’s negative, go down.
Examples:
For the ordered pair (-4,3), start at the origin and move 4 to the left and 3 up to plot the point.
For the ordered pair (-5, -2), start at the origin and move 5 to the left and 2 down.
For the ordered pair (0, 5.5), start at the origin, don’t move left or right, go up 5 and 1/2 (that’s between two lines).
The 4 Quadrants
Even young kids learn to plot two positive numbers in the first quadrant; however, it gets trickier when points are located in all four quadrants. Quadrants are usually named with Roman numerals. It seems backwards to kids because quadrant I is the top right section and then it goes counter-clockwise.
Quadrant I: top right (+,+)
Quadrant II: top left (-,+)
Quadrant III: bottom left (-,-)
Quadrant IV: bottom right (+,-).
The first thing to do is make sure kids understand where points should end up. If the ordered pair they’re plotting is, for example, (-5, 7), it will end up in quadrant II.
Hands-On Activity
If you have room, make a large coordinate grid on the floor with masking tape. Give each student a card with a point on it and have them locate their points on the floor grid.
Free Printable
Math Warehouse: Create, save and print custom-made graph paper.
Teacher Image: Coordinate and Number Facts Game that kids enjoy.
Teaching Image: Practice sheet for plotting coordinates
Create Pictures
If you teach this skill before Open House, you can make a colorful wall display with the pictures the students have created.
Math-Aids: Create customized 4-quadrant graphing puzzles
Super Teacher: Plot “Father Christmas” picture in quadrant one only
Super Teacher: Plot a robot
Worksheet Works: My favorite because you can create random pictures to plot
Conserve Turtles: “What Endangered Animal?”
Remember! the best pictures are the ones that students design themselves! They can swap pictures with friends.
Computer Games and Challenges
IXL: Plot points on a coordinate grid. Can be used as whole-class activity or individually if students have computer access
Fun Brain: Students identify given points on “What’s the Point?”
National Library of Virtual Manipulatives: Battleship Game
image credit: Wikimedia Commons; Author, Pearson Scott Foresman
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