“乘法分配律”是小学四年级下册的教学内容。教材是从解决36页例3“负责挖坑、种树的一共有多少人?”这一问题出发,让学生用每组的人数乘组数,即(4+2)×25;也可以分别算出挖坑、种树的人数与抬水、浇树的人数,再相加,即4×25+2×25。然后让学生意识到两种算 “Multiplication distribution law ” is the fourth grade of primary school teaching content. The textbook starts from solving the problem of “how many people are responsible for digging and planting trees?” On page 36 of Example 3, and allows students to multiply the number of people in each group by (4 + 2) × 25 We can calculate the number of people digging, planting trees and carrying water, the number of trees, and then add that 4 × 25 +2 × 25. Then make students aware of two kinds of calculations