一、乘法交换律要教吗乘法的初步认识是二年级数学上册的教学内容,人教版课本第48页呈现5+5+5=15,5×3=15或3×5=15。从课本中乘法的定义可知,3+3+3+3+3=15,是用乘法5×3=15或3×5=15表示,也就是3×5与5×3都可以表示成3个5相加或者5个3相加。这样的乘法定义,已经规定了5×3=3×5,无需验证,也无需再学习乘法交换律。四年级数学下册第24页呈现4× First, the multiplicative exchange law to teach? The initial understanding of multiplication is the teaching content of the second grade mathematics, the PEP 48 page presents 5 +5 +5 = 15,5 × 3 = 15 or 3 × 5 = 15. We can see from the definition of multiplication in the textbook that 3 + 3 + 3 + 3 + 3 = 15 is represented by multiplication 5 × 3 = 15 or 3 × 5 = 15, that is, 3 × 5 and 5 × 3 can be expressed as 3 Add 5 or 5 3 together. Such a definition of multiplication, which has been specified 5 × 3 = 3 × 5, without verification, and no need to learn the multiplication exchange law. Fourth grade mathematics book page 24 rendering 4 ×