Imperial Rulers
Completion requirements
Lesson 1: Measurement Systems - Imperial Rulers
Constructing Knowledge
The other side of the ruler shown earlier is used to measure in inches. Inches are subdivided differently than centimetres — each subdivision for an inch is half the size of the previous one.
Take a look at the section between 2 and 3 inches. (Note: The following diagrams are not drawn to scale.)
Lines labelled with whole numbers are inch measurements. When the inch is cut in half, there are two half inch sections.
When both of those half-inch sections are cut in half, there are four quarter inch sections, as shown in the diagram below. The 2/4 measurement can be reduced to 1/2, which was used in the previous diagram.
When each of those quarter-inch sections are cut in half, there are eight eighths of an inch sections, as shown in the diagram below. Many of these fractions can be reduced.
Most rulers divide the sections one more time to give sixteenths of an inch, as shown in the diagram below. And once again, many of the fractions can be reduced. c
Most rulers don't show all of these fractions because, as you can see, such a ruler would be very cluttered. However, it is possible to determine which denominator to use by looking at the length of the subdivision line, as shown in the diagram below. By counting the number of lines of that length, or longer, from the inch mark, you can determine the numerator.
