Double Number Lines

Double Number Lines

Introduction to Double Number Lines

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Introduction to Double Number Lines

Read and Discuss

A company will enlarge 5-inch-by-7-inch photographs to any size you want.

You can use a double number line to help you see some of the possible photograph sizes.

  • To make a double number line, you start with two number lines and line them up at 0.
  • You know that the ratio of the width of the original photograph to its length is 5:7, so you would make one tick mark on the top line at 5 and another tick mark on the second line at 7, making sure that the 5 and 7 are lined up.
  • Now you can add other numbers to the number lines.
  • What are some of the possible photograph sizes you can order?
  • What is another pair of numbers that would line up on this double number line?
  • What does each lined-up pair of numbers represent? (Think of the question from the problem.)
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