What is the probability that at least two people born in March will have the same birthday? A（30×29）/31² B 1-（30×29）/31² C 1/31 D 2/31

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• 1. Randomly investigate the birthdays of 100 people (including the elderly, young and middle-aged, children, etc.), and find out the probability that two of them have the same birthday (can be different years)
• 2. When a boat finds a leak, it has entered some water, and the water enters the boat at a constant speed. If 10 people clean the water, it will finish in 3 hours; if 5 people clean the water, it will finish in 8 hours. If it is required to finish in 2 hours, it should be arranged___ A man washes for water
• 3. If a work is done alone, Party A can complete it two days ahead of schedule. Party B can complete it three days ahead of schedule. Now, after two days of cooperation, Party B will continue to do the rest alone, just in time. If cooperation, how many days will it take to complete the project?
• 4. For a project, Party A and Party B work together for 20 days, and Party A has worked together for 2 days after 3 days to complete 1 / 5 of the whole project. How many days does it take for Party A and Party B to work alone? Remember, ”Three days later, it was followed by "three days later, B followed". Just understand.
• 5. For a project, Party A will do it alone in 15 days and Party B will do it alone in 20 days. After three days of cooperation between the two teams, team B will do the rest of the project alone. How many more days will it take to complete? -------------------------------------------------------------------- Please send the formula and solution to me if you know the answer,
• 6. Several simple primary school mathematics calculation problems What can be calculated simply should be calculated simply: 11.58-（5/11+1.58） 24*（1/3+8/3+7/12） 120.8*3/4-0.8*3/4 99 * 97 / 98 thank you {(this symbol means multiplication *) (/ followed by denominator)
• 7. Non application questions on prime numbers Fill in the appropriate prime number in the brackets to make the formula true! 98=(）X（）x（） 100＝（）x（）x（）x（）x（） 110＝（）x（）x（） 112＝（）x（）x（）x（）x（） 114＝（）x（）x（）x（）
• 8. 1. A section of road AB is 240 meters long. A starts from a to B. half an hour later, B starts from B to a at the speed of 36 km / h. When a and B meet, the time ratio of a and B is 6:5, 2. The price ratio of a and B is 7:3. After the price rises by 70 yuan, the price ratio is 7:4. How much is the original price of a and B? 3. There are two kinds of apples, the price ratio is 5:4 and the weight ratio is 2:3. After mixing the two kinds of apples into 100kg, the unit price is 4.4 yuan per kg. How much is the original unit price? It's better to solve it by arithmetic
• 9. Seek master solution elementary school mathematics application problem ~! Urgent~~~~~~ Lele drinks a glass of milk in four times. For the first time, he drinks 1 / 5 of a glass, and then fills it with water. For the second time, he drinks 1 / 4 of a glass, and then fills it with water. For the third time, he drinks 1 / 2 of a glass, and then fills it with water. For the fourth time, he drinks it all in one gulp. Does Lele drink more milk or more water
• 10. In a hurry! Answer in half an hour! Elementary school mathematics sixth grade score application problem! There are two piles of coal a and B. pile a is 120 tons more than pile B. If 25 tons are transported from pile B to pile a, the weight ratio of pile AB is 5:3. How many tons of coal are there in pile a and pile B?
• 11. The probability of two out of 50 having the same birthday 365 days
• 12. What is the probability that at least two of n people have the same birthday?
• 13. 1. There is a chain made of red, white and black beads in the order of five red, four white and three black beads, sharing 185 beads. How many are the black beads? What color is the 69th?
• 14. What are the wide angles of mathematics from the second volume of the first grade to the second volume of the sixth grade of PEP? Write clearly!
• 15. Wide angle mathematical problems in sixth grade mathematics 1. For any seven different natural numbers, the difference between at least two of them is a multiple of 6. Why? 2. In 1,2,3,..., 49,50, at least how many different numbers must be taken out to ensure that one of them can be divided by 5? 3. There are 63 students in a class. They all participate in extracurricular interest groups. The activities include mathematics, art, calligraphy and English. Each student can participate in one, two, three or four interest groups. How many students in the class participate in the same project? 4. Give 400 cards to several students, each of whom can get no more than 11 cards. Try to prove that at least 7 students get the same number of cards How many questions can I answer? I'm in a hurry. I'm in a hurry. I'm in a hurry. I'm in a hurry
• 16. ① Eight chickens and 15 rabbits have () feet ② () chicken and 6 rabbits have 36 feet ③ The chicken and the rabbit have 48 feet ④ How many rabbits and chickens are there in the cage,
• 17. On the Inner Mongolia prairie, there are a group of herdsmen driving a group of cattle and sheep, people and cattle. There are 27 sheep and 100 legs at the same time. How to calculate the number of people, cattle and sheep
• 18. Practical problems in grade four of primary school The two cars left from the two places at the same time and met them two hours later. At this time, they were 20 kilometers away from the midpoint of the two places. It is known that car B travels 60 kilometers per hour and car a how many kilometers per hour
• 19. Next to a straight runway, 51 flags were planted, with an interval of 2 meters. Later, only 26 small flags were planted, with an average interval of how many meters? (both ends are inserted)
• 20. A and B plant trees. It takes 13 more time for a to plant this batch of trees alone than B. if they work together, B will plant 36 more trees than a when they finish the task. How many trees are there in all?