Step 1: In the initial stage of learning to calculate, children will put objects together and break their fingers. After mastering the movements, they can quickly put out the process of addition and subtraction.

Step 2 Image: In the process of children's learning, try to guide children to add and subtract in order. For example, fingers can be added and subtracted in sequence, which can be 4+5=9. How about 5+4? Ask your child why, guide him to think backwards and practice repeatedly, and he will feel that mathematics is diverse and not boring.

Step 3: Abstraction: In the process of sequential thinking, play with children in different ways gradually, and solve problems without fingers and eyes, so that children can have a process from image to abstraction.

The first way, each box of 4 yuan, 92*4=368 yuan;

The second way, each box of 30 yuan (10 box), 92 children, buy 10 box, * * 300 yuan;

The third way, each box of 40 yuan (16 boxes), 92 children, buy 6 boxes, * * * 240 yuan.

The third way, purchasing milk is the cheapest.