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Geometry

# GED Mathematical Reasoning: Reading Rulers

Example 1

State the length of the pencil in inches:

Rulers can come in all shapes and sizes. They can include only Metric units, only Standard units or both.

In Example 1, we’ll refer to the diagram of a 6 inch ruler – as you see in Example 1 –  containing inches and centimeters.

Let’s focus on the side labeled “inches” – the BOTTOM portion of the ruler.

Most inch rulers are labeled in increments of one inch. Notice on our ruler that each one inch increment is labeled 1, 2, 3, and so on.

Also notice that every inch is broken down into 16 smaller increments. And each fraction of an inch is represented by a mark of a different height.

Shorter than the one-inch mark is the one-half inch mark. Slightly shorter than that is the one-fourth inch mark. Slightly shorter than that is the one-eighth inch mark. The smallest unit of measure on the inch ruler is one-sixteenth of an inch.

To state the measure of the pencil in Example 1, we’ll first determine the number of whole inches the pencil measures. Then, we’ll identify the fractional part of an inch that it measures.

Looking at the diagram, we see that the pencil measures 3 whole inches plus a little bit more. The fractional part of an inch that it measures is one-eighth of an inch.

So we will state the measure of the pencil to be three and one-eighth inches.

Example 2

State the length of the pencil in centimeters:

In the Metric system, short distances are measured using centimeters. Most centimeter rulers are labeled in increments of one centimeter. Notice on our ruler that each one centimeter increment is labeled 1, 2, 3, and so on.

It is also important to note that each centimeter is divided into 10 millimeters.

So to state the length of the pencil shown in Example 2, we’ll first determine the number of whole centimeters the pencil measures. Then, we’ll identify the number of millimeters that it measures.

The pencil measures seven whole centimeters and two millimeters.

And it is common to state the answer in one of two ways.

The first way is using centimeters and millimeters as:  7 centimeters and 2 millimeters.

7cm 2mm

The second way we can state our answer is as a decimal using centimeters only, which would be: 7-point-2 centimeters.

7.2cm

As a final note, when working with measures as small as fractions of an inch and millimeters, it can be difficult to see an exact measure. It is important, however, to be as accurate as possible with our measurements.

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