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Comparing Lengths: Longer and Shorter

This lesson explains how to compare the length of two or more objects by lining them up and describing them as longer, shorter, or the same length. It also covers comparing lengths indirectly using a third object, and ordering several objects from shortest to longest with easy visual examples.

Introduction

Before we can measure length with numbers, we first learn how to compare lengths just by looking, lining objects up, and describing what we see. Comparing lengths means deciding whether one object is longer than, shorter than, or the same length as another object.

What does it mean to compare lengths?

Length tells us how long or how short something is, from one end to the other. When we compare lengths, we look at two or more objects and decide which one stretches out further. We use three key words:

Longer: an object that stretches out more than another object.
Shorter: an object that stretches out less than another object.
Same length: two objects that stretch out exactly the same amount.

This idea is closely related to comparing other properties of objects, such as in long and short, where we first learn these describing words with everyday objects.

Comparing lengths directly

The easiest way to compare two lengths is called direct comparison. To do this, we place two objects next to each other so that one end of each object lines up exactly. Then we look at the other end to see which object goes further.

Both ribbons start at the same dashed line, so we can directly see that Ribbon B is longer than Ribbon A.

Because both ribbons start at the same dashed line, we can see right away that Ribbon B reaches further than Ribbon A. So Ribbon B is longer, and Ribbon A is shorter. If both ribbons ended at the exact same spot, we would say they are the same length.

Comparing lengths indirectly with a third object

Sometimes two objects cannot be placed next to each other. Maybe they are too far apart, or one is taller than a wall. In these cases, we use a third object, like a piece of string, a strip of paper, or a stick, to help us compare.

Here is how it works:

Use the third object to measure the length of the first object, for example by cutting a string to match its length.
Take that same string and place it against the second object.
If the string is shorter than the second object, the second object is longer than the first. If the string is longer, the second object is shorter. If it matches exactly, the two objects are the same length.

This method, called indirect comparison, is useful any time two objects cannot be lined up side by side.

Ordering objects from shortest to longest

Once we can compare two objects, we can also compare three or more objects and put them in order. To do this, we compare each object to the others and arrange them from the shortest to the longest, or from the longest to the shortest.

Each pencil is lined up at the same starting point, showing the order from shortest to longest: Pencil 1, Pencil 2, Pencil 3.

Notice that all three pencils start at the same dashed line. This makes it easy to see that Pencil 1 is the shortest, Pencil 2 is longer than Pencil 1 but shorter than Pencil 3, and Pencil 3 is the longest of the three.

Tips for comparing lengths correctly

Always line up one end of each object before comparing the other end.
Compare objects on a flat, straight surface so the lengths are not bent or curved.
When using a third object to compare indirectly, make sure it does not stretch or bend between measurements.
Use the words longer, shorter, and same length carefully, since each one describes a different result.

Comparing lengths is one of several early comparison skills. Similar ideas apply when we compare weight in light and heavy, or compare how much a container can hold in holds more and holds less. Practicing all of these comparison skills together helps build a strong foundation for measurement.

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Math 1