I'd like to ask some math questions for high school students, 1. The gravitational force F between a satellite and the earth is given by the formula F = GMM / R, where m is the mass of the earth and G is a constant 2. During the summer vacation, a travel agency launched the following method of group formation: for groups with 100 people, each person charges 1000 yuan. If the number of groups exceeds 100 people, the average charge per person will be reduced by 5 yuan for each more than one person, but the number of groups can not exceed 180 people. How to form a group, but the travel agency charges the most? 3. The area of a certain type of printing paper is 623.7cm square, and the margins of the upper and lower pages are required to be 2.54cm respectively, and the margins of the left and right pages are required to be 3.17cm respectively. If vertical printing is required, what is the length and width respectively to make the maximum printing area (accurate to 0.01cm)

1, which is the derivative of F = GMM / R, so the instantaneous rate of change = - GMM / (R ^ 2)
two point one zero zero