Current location - Training Enrollment Network - Mathematics courses - 20 1 1-20 12, Nan 'an District, Chongqing, There are 26 questions in the last line of seventh grade mathematics.
20 1 1-20 12, Nan 'an District, Chongqing, There are 26 questions in the last line of seventh grade mathematics.
26. As shown in figure 1, it is a local street map of a city, with six directions. If you walk from A to B (you can only walk from north to south or from west to east, as shown by the arrow in the figure), how many different ways are there? In order to solve this complicated problem, students may wish to do the following exploration and try to find out the law and then solve the problem. (Note: The following can only be from north to south or from west to east)

(1) Try: Count different moves in simple graphics.

① When there are two roads in some streets in this city, as shown in Figure 2, please count them and directly answer how many different ways to get from A to B?

A:

② When there are three roads in some streets of this city, as shown in Figure 3, please count them carefully and directly answer how many different ways to get from A to B?

A:

(2) Induction: Statistics the process characteristics of different moves of simple graphics, and form a conclusion. What are the rules for finding out how many different ways to walk from A to B in Figures 2 and 3?

A:

(3) Simple application: (Requirements: show the process of finding different ways in the diagram, and then answer the results directly)

① How many different ways are there to walk from A to B in Figure 4?

A:

② How many different ways are there to walk from A to B in Figure 1?

A:

(4) Expand the application: (Requirements: show the process of finding different ways in the diagram, and then answer the results directly)

When some streets in the city become as shown in Figure 5, how many different ways are there to walk from A to B?

A: