Reading a Scale with Decimal Intervals: Lesson for Kids

Instructor: Mark Boster
The word 'scale' has many different definitions, like the scales on a fish and when you scale a mountain. In math, the term 'scale' means something entirely different. In this lesson, learn how to read a scale with decimal intervals.

What is a Scale?

Leona bought a thermometer. It was hot outside and she wanted to know the temperature. When she hung it in her backyard, she noticed that the numbers on the thermometer were out of order and different distances from each other. It was not very helpful!

You see, Leona's thermometer did not use a scale. A scale is a set of numbers or marks that are the same distance from each other, and it's used to measure the level of something. Generally, all measuring devices use a scale of some sort.


Look at the two thermometers in the image. The thermometer on the left does not use a scale--the numbers are random and are not the same distance from each other. The thermometer on the right DOES use a scale--the numbers are in order and the same distance from each other, so they can be used for measurement. Leona needs to return her thermometer for one that uses a scale if she wants to read the temperature!

Scales with Decimal Intervals

Scales are used to read temperature on thermometers, but where else can you find scales? They're found in many aspects of math to compare and measure, like rulers and number lines. Often, these scales have markings for whole numbers, and they go in order from least to greatest.

Scales may also have smaller markings for portions of those whole numbers. These are decimals of the whole number, and the decimals also go in order from least to greatest. For instance, a scale that has markings for tenths would show markings that stand for 0.1, 0.2 , 0.3, 0.4, 0.5 and so forth. The space in between a set of these markings is called a decimal interval. So, for our 0.1, 0.2 , 0.3, 0.4, 0.5... scale, the decimal interval would be one-tenth. If we cut each of those into ten intervals, we would have hundredths.

Now, let's take a look at some common math tools that use scales with decimal intervals.


Rulers have measurement lines on them that are all equal distances apart, so they use scales.

A common ruler used in classrooms

Look at the scale of the ruler in the image. The numbered lines represent centimeters, and they are all equal distances from each other. The little lines in between are also equal distances apart, and they represent millimeters. A millimeter is one-tenth of a centimeter. That means the decimal interval on this ruler is 0.1 of a centimeter. So, if you started at the 2 and counted up, you would have 2.0 centimeters, 2.1 centimeters, 2.2 centimeters, 2.3 centimeters and so on.

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