The answer process is as follows:

(1)5, 9, 10, 18, 15, 27, so it is difficult to find a rule.

(2) Transformation: 5, 10, 15 (the first item, the third item and the fifth item are extracted), and the laws are all multiples of 5. It is 2 and 3 times of 1 and 5 in turn.

(3) Transformation: 9,18,27 (the second, fourth and sixth items are extracted), and the laws are all multiples of 9. It is 2 and 3 times of 1 9 in turn.

(4) So the number after 27 is four times that of 5, which is 20. The one behind 20 is four times that of 9, which is 36.

Extended data:

Find a routine method:

1. Generally, it is necessary to observe the characteristics first, and then check several commonly used methods in turn, such as the difference and the operational relationship between adjacent three items. If the number changes dramatically, you can consider the square sum cube, and be familiar with some commonly used square sum cube values.

2. To find a regular topic, we usually give a series of quantities in a certain order, which requires us to find a general law according to these known quantities. Find out the rule, usually the serial number of the package. Therefore, it is easier to find the mystery by comparing variables with serial numbers.