Page 49: 1, (nitrogen) (78) (carbon dioxide and other impurities) (0.06) 2, (0.2 1) 3. A: I can also know that the air contains 2 1% oxygen. 1, (30)(24)(54)( 12) 2, (2 1)( 17) How many people like other books? 50× 6% = 3 (people) A: There are 3 people who like other books. Page 50: 1, 1, (7)(3)(7) 2, (6)(4) 2. A: The modes of this set of numbers are 5.3. 1, (46)(48), 2, (42)(36) 3. 2, 1, mode: 40, median: 40, average: 40.4. 2. A: It is more appropriate to use the median. 3. Median: 3800, average: 5980, 2, A: Median is more appropriate. 3. A: Because the income of the two families is too high, it has increased a lot on average.