1. A trip to St. Petersburg is being organized for 30 schoolchildren along with their parents, some of whom will be driving cars. Each car can accommodate 5 people, including the driver. What is the minimum number of parents that need to be invited on the trip?

ANSWER: 10
Solution: No more than 4 students can fit in a car, so 8 cars will be needed, i.e., 10 drivers.