Order Objects by Length

Students compare and arrange three objects from shortest to longest using direct and indirect length comparisons.

Review Longer and Shorter

Length tells how long an object is from one end to the other. When we compare two objects, we can use the words longer and shorter. Look at a crayon and a pencil. Place them so their left ends start at the same spot. If the pencil reaches farther to the right, the pencil is longer than the crayon. The crayon is shorter than the pencil. An object may look bigger because it is placed higher or lower, so always check its two ends. We can also say two objects are the same length if both ends match when the objects are lined up. Remember: longer means an object reaches farther from the shared starting point, and shorter means it does not reach as far.

Compare Two Objects Directly

A direct comparison means putting two objects next to each other to compare their lengths. Suppose you want to compare a blue ribbon and a red ribbon. Lay both ribbons straight on a table. Line up their left ends exactly. Do not let either ribbon bend or curl. Now look at the other ends. If the blue ribbon reaches farther, it is longer than the red ribbon. The red ribbon is shorter than the blue ribbon. It is important to line up one end because ribbons placed at different starting points can trick your eyes. You can directly compare pencils, strips of paper, blocks, or other objects that can be moved beside each other.

Use a Third Object to Compare

Sometimes two objects cannot be moved next to each other. We can compare each one with the same third object. Imagine a bookshelf and a desk are in different rooms. Use one piece of string as the third object. First, stretch the string straight along the bookshelf. The bookshelf is shorter than the string because it does not reach the string's end. Next, take the same string to the desk and line up one end. The desk is longer than the string because it reaches past the string's end. Since the bookshelf is shorter than the string and the desk is longer than the string, the desk is longer than the bookshelf. The same string must be used without cutting or stretching it.

Order Three Objects by Length

To order three objects by length, arrange them from shortest to longest. Suppose you have a yellow straw, a green straw, and a purple straw. Place all three straws straight and line up their left ends. Look for the straw that reaches the least distance. Put the yellow straw first because it is the shortest. Next, find the straw that reaches farther than the yellow straw but not as far as the purple straw. Put the green straw second. Put the purple straw last because it reaches the farthest and is the longest. The order is yellow, green, purple. You can check your work by making sure each object is longer than the object before it.

Explain the Length Order

After ordering objects, explain how you know the order is correct. Use comparison words such as shorter than, longer than, shortest, and longest. For example, three paper strips are ordered orange, blue, and pink. You can say, “The orange strip is the shortest. It is shorter than the blue strip. The blue strip is longer than the orange strip but shorter than the pink strip. The pink strip is the longest.” This explanation compares neighboring objects and names the two ends of the order. You can also point to the shared starting line and show where each strip ends. A clear explanation tells what you noticed and uses length words correctly. Check that all three strips are straight and begin at the same point.