6.1. A ticket to the Historical Museum costs 300 rubles for an adult and 60 rubles for a schoolchild, while pensioners can visit the museum for free. There is also a 
"family ticket" for two adults and two children, which costs 650 rubles. What is the minimum amount in rubles that a family, including a father, a mother, a grandmother-pensioner, and four schoolchild children, should pay for visiting the museum?
Solution. All possible options are presented in the table.

| Grandmother | Father | Mother | 1st child | 1st child | 1st child | 1st child | Total cost, RUB |
| :---: | :---: | :---: | :---: | :---: | :---: | :---: | :---: |
| free | "adult" ticket 300 | "adult" ticket 300 | "child" 60 | "child" 60 | "child" 60 | "child" 60 | 840 |
| free | "family ticket" 650 |  |  |  | "child" 60 | "child" 60 | 770 |

The minimum amount that a family, including a father, a mother, a grandmother-pensioner, and four school-age children, should pay for visiting the museum is 770 rubles.

Answer: 770 rubles