Math Background

Coordinate Graphing: When Students Ask

  • Why should I bother learning this?
    Encourage students to think of uses for grids, such as locating a town on a state map or finding a street address in a city. They should see that locating the coordinates of a point on the coordinate plane is like following directions to find a street address, if you know the street name and number and have a detailed map. You might also point out that it's easier for many people to see the relationships between numbers when they're shown in a picture.
  • Isn't this just the same as a line graph?
    Provide some sample line graphs along with the coordinate graphs your students are working on. Point out that a line graph does use some of the same ideas as a coordinate graph, such as showing the relationship between two different sets of numbers with points connected by lines. Point out that there are some differences; for example, line graphs show change over time, while coordinate graphs show the relationship between two numbers without saying anything about the meaning of the numbers.
  • Why can't I put the numbers in either order?
    Ordered pairs can be very confusing for students. It's essential to reinforce the importance of the order of the coordinates. The best way to answer this question is to give lots of examples, showing how reversed pairs don't mean the same thing. To help students remember which coordinate is named first, tell them that just as x comes before y in the alphabet, the x-coordinate comes before the y-coordinate in an ordered pair. Maps are useful here as well. Use a map and ask students to find a town in a given square of the map. Then reverse the coordinates and ask the students if the same town is at those coordinates. This gives a practical, real-world example of why order is important!

Houghton Mifflin Math Grade 4