A ruler is a device that is used to measure the lengths. There are two types of rulers. One is the Metric Rulers and the other one is the English Rulers. The Metric Rulers are the easiest to read as there is no much complication. The markings in the metric rulers are in millimeters and centimeters. So you will not be dealing with much of the fractions as in the case of the English rulers. In a metric ruler the smallest marking are in the millimeters. The largest lines indicate the centimeters. You should know that 10 millimeters make one centimeter. For example if you mark 6 millimeters after the 3rd centimeter then the measurement you have taken would be 3.6 centimeters.
In the English rulers you will be dealing with inches. It is one of the difficult rulers to read. You will be dealing with fractions mostly. Each marking in an English ruler would be 1/8th of an inch or 1/16th of an inch depending on the type of ruler you have chosen. This indicates that some of the English rulers have 8 divisions in an inch and some have 16 divisions in an inch.
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