The learning method is reported to the people's education edition, the sixth grade, the 34 th answer to mathematics.

The exercise on page 34 of the second volume of the sixth grade mathematics of People's Education Press is:

Apply the basic properties of proportion to judge which two proportions in the following groups can constitute proportion.

(1) 6: 3 and 8: 5

(2) 0.2: 2.5 and 4: 50

(3) 1/3: 1/6 and 1/2: 1/4.

(4) 1.2: 3/4 and 4/5: 5

The solution to this kind of problem is to apply the basic nature of proportion. On the same page of this textbook (page 34), the basic nature of proportion has been summarized, that is, "in proportion, the product of two external terms is equal to the product of two internal terms."

According to this property, it can be judged as follows:

( 1)

The product of external terms is: 6×5 = 30.

The product of internal terms is: 2 x 8 = 24.

Because the two products are not equal, the two ratios are not proportional.

(2)

The product of external terms is: 0.2 x 50 = 10.

The product of internal terms is: 2.5×4 = 10.

Because the two products are equal, the two ratios are proportional.

(3)

The product of external terms is:1/3x1/4 =112.

The product of internal terms is:1/6x1/2 =112.