11.2. In the quarry, there are 120 granite slabs weighing 7 tons each and 80 slabs weighing 9 tons each. A railway platform can load up to 40 tons. What is the minimum number of platforms required to transport all the slabs?
Answer: 40 platforms

It is impossible to load 6 slabs onto one platform, even if they weigh 7 tons each. Therefore, at least $200 / 5=40$ platforms are needed. Forty platforms are sufficient: on each platform, you can load 3 slabs weighing 7 tons and 2 slabs weighing 9 tons.

Comment. The necessity of at least 40 platforms is justified - 3 points. An example of distributing the slabs on 40 platforms is provided - 3 points.