There are 1, 2, 3 ... 20 10 natural numbers on the blackboard. The rules for operating them are as follows: erase three numbers at a time and add the single digits of the sum of the erased three numbers. If two numbers are found on the blackboard after the operation of 1004, one is 19 and the other is. One is the given 19, and then the other is the number from 1 to 20 10 and then divided by 19. The answer is: 202 1036. Calculation method: 2010 * (2010+1)/2-19 = 2021036 2. The fourth floor takes six seconds. How many seconds does it take to run to the eighth floor at the same speed? 3. A group of children are brother and sister, and the two chat casually. The younger brother said that he had one more brother than his sisters. So, how many brothers does my sister have than my sisters? Xiaoming poured water into a water tank with a bottom area of 24x 18cm and a height of 30cm, accounting for two thirds of its volume. He is a curious boy and wants to know the volume of the lead block he just bought. After the lead block was put into the water tank, the water level rose to 22 cm. What is the volume of lead block? Answer: 2 questions: 8 seconds; 3 questions: 3; Question 4: 864

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