Original price of children's encyclopedia 156 yuan. Under the discount of buying 4 sets for free 1 set, buy 15 sets at one time and prepare 1872 yuan.

The solution is as follows:

Buy 4 sets and get 1 set. According to the meaning of the question, you can buy 5 sets of children's encyclopedias at the price of 4 sets.

4 x 156 = 624 yuan, you can buy 5 sets.

15 ÷ 5 = 3 (that is, 15 sets equals 3 sets and 5 sets).

3 x 624 = 1872 yuan.

Think about solving problems:

(1) Find the price of 4 sets. Because of the discount, you can actually buy five sets at this price.

(2) The15 set is actually three of the five sets. The above price multiplied by 3 is the total price.