Cross method can be used to calculate the concentration of solution, such as dilution, concentration or mixing of solution. Using this method, the problem-solving process is simple, fast and correct. The following example introduces the principle of crossover method.

The percentage concentrations of solution A and solution B of the same substance are A% and B% respectively B %(A% > B%). Now, these two solutions are used to prepare a solution with a percentage concentration of C%. What is the mass ratio of these two solutions?

For the solution of the same substance, the mass of solute before and after preparation is equal, which can be solved by this principle.

Let a and B take m 1 and m2 grams respectively, and the mass of the mixed solution is (m 1 m2). M train

1A% M2b% = (m 1m2) C% Put this formula in order: m 1m2=c-ba-c, and m 1m2 is the mass ratio of the two solutions.

In order to facilitate memory and operation, if C replaces A, C replaces B, C replaces C, and M replaces m 1, M.

Sparse instead of m2, write the above formula in the general form of cross method, as shown below:

In the figure, the concentration of m and the dilution of m are the mass ratio of solution A to solution B..

This operation method is called crossover method. When calculating with the cross method, we should pay attention to finding the difference sideways and looking at the result sideways.