From the title, we know that two radishes for six carrots and nine radishes for three Chinese cabbages can be simplified as: 1 radish for three carrots and three radishes for 1 Chinese cabbage. At this time, we write the relationship between radish, carrot and Chinese cabbage.

1 root radish =3 carrots 1 Chinese cabbage =3 radishes. According to observation, 1 Chinese cabbage =3 radishes =9 carrots.

The relationship is 1 Chinese cabbage =9 carrots, so 5 Chinese cabbages can be replaced by 5×9=45 carrots.

The difficulty of this problem lies in finding these two relationships: 1 root radish =3 carrots, 1 Chinese cabbage =3 radishes.

The solution to this problem is to find the exchange relationship among Chinese cabbage, radish and carrot. If the number given in the problem can be simplified, simplify first and then find the relationship. The key is to find the relationship between the left and right sides of the equal sign. This kind of question is often to find an intermediate object to exchange, and you need to observe to get the answer.

Extended data:

Equal to:

To solve the problem of commodity exchange, it is necessary to find out whether there is a relationship between the commodities on the left and right sides of the equal sign and what is the relationship.

Mathematically, two mathematical objects are equal if they are the same in all aspects. Generally speaking, equality is constructed by the equivalence relationship between two elements. Connect two expressions with an equal sign to form an equation.

An equation that holds under any conditions is called an identity, and an equation that contains unknowns is called an equation.