That is, how to save money is reasonable. Let's calculate first. If you don't buy group tickets, adults buy adult tickets and children buy children tickets, then it should be 30* 15+30* 10=750 yuan. If all tickets are purchased, it is unreasonable that children only want 10 yuan, while the group wants 20 yuan. Therefore, we only need to give 5 children out of 30 to adults, and it happens that each adult can save 10 yuan, so the total amount of money needed is 20 * * * 25 * 10 = 650 yuan.
This method uses the least money, so it is also the most reasonable. From this question, we can tell children that when we usually do things (use money), we should calculate what kind of methods can not only do things well, but also save resources.