Write the length of the line as a decimal.
A decimal number is a number with a decimal point in it. This comes in between the ones digit and the tenths digit. And it’s a way of separating part of a number that represents the whole and the part that represents less than a whole. We can identify both of these on the ruler. Each of the longer lines shows a whole number of inches, from zero up to eight. And each of the shorter lines in between show the part of an inch. Let’s use this information to measure the line.
Firstly, we can see that the whole number part of our decimal is going to be three. But how many tenths are there? Now, we might expect our ruler to be divided into tenths. But if we count carefully, we can see that there are eight divisions in between each whole number. It’s divided into eighths.
So although we can’t just count the number of notches, what we can do is look at where the end of the line is. It is halfway between three and four. How many tenths are the same as a half? Five tenths are the same as a half. And so, the length of the line written as a decimal is 3.5 inches.