(2011年12月)“大树有多高”是小学数学课本六年级(上册)中的一个标题。内容是:在阳光下,根据竿高和影长的关系,运用正比的规律,测算树的高度(以下简称测树高)。过去的算术教材中,在“比的意义”这个单元中,也有这个内容。那时的定论是:“在同一时间内,竿高和影长成正比。”并附有插图。由于没考虑实用价值,故没有要求实地测算。新版数学教材,为了体现知识的实用性,对它动 (December 2011) “How Tall Trees Are” is a title in the sixth grade of elementary school mathematics textbooks (first volume). The content is: In the sun, according to the relationship between pole height and shadow length, using the law of proportionality, calculate the height of the tree (hereinafter referred to as measuring tree height). The past math textbooks, in the “meaning” than “this unit, also have this content. At that time the conclusion is: ”At the same time, pole height and shadow length is proportional. " And with illustrations. As no practical value was considered, no field calculations were required. New mathematics textbooks, in order to reflect the practicality of knowledge, it move