The first grade math measurement tool is a ruler. Under normal circumstances, I will buy a set of rulers for my children, including a ruler, a triangular ruler and a protractor. When I was a freshman, I basically used a ruler and bought a ruler with a length of 20 cm. Pupils can use it to draw straight lines, line segments and straight lines when doing math homework.

Why choose a 20 cm math exercise book? The small exercise book is 20 cm long and 15 cm wide. In order to draw the longest line in the exercise book, you need a ruler of at least 20 cm.

Rulers are indispensable mathematical tools, so they must be left to students when they go to school. Rulers, also known as rulers and scales, are tools for drawing line segments (especially straight lines) and measuring length. There are usually scales on the ruler to measure the length.

Daily protection of rulers:

1, first of all, use the ruler correctly. For example, it is best not to use a plastic ruler when delineating materials, which will easily scratch. There are also many people who will make a mistake, that is, they will draw lines quickly, and then they will draw along the ruler because of its slippery characteristics, which will blur the graphics, so the speed is moderate.

It's best not to mix a ruler with a knife or metal stationery. When mixing with pens, be sure to cover the pen cover.

3. The ruler has a sharp part, so be careful when using it to avoid scratches.

4, be sure to prevent exposure and long-term sun exposure, away from the fire source, so as not to affect the accuracy of the instrument and cause danger.

5, it is best not to clean with a brush, which means try not to dirty the ruler.