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There are five students, each said a number, add up to an odd number. How many people said odd?
It's all possible
We can know by category discussion
In table tennis competition, four players from a, B, and d play one game every two. As a result, a wins D, and a, B and C win the same number of games. How many games does Ding win? Four players, a, B, C and D, play table tennis once every two. As a result, a wins Ding, and a, B and C win the same number of games,
① Suppose that a, B and C win 1 game.
Five students from a, B and C have played table tennis. It is stipulated that every two students should play one game. So far, four matches have been played in a match and three games have been played in B, There are two matches in the third round and one in the fourth match, so it is a match The three side areas of a cuboid are 6, 8 and 12 respectively. The volume of this cuboid is ()
Five students from a, B, C and d play table tennis. It is stipulated that every two students have to play one game. So far, four games have been played in a game, three games have been played in Party B, two games have been played in game C, and one game has been played in Ding
The three side areas of a cuboid are 6, 8 and 12, and the volume of this cuboid is (24)
A, B, C, D and E are playing table tennis every two. Now that a has played 4 games, B has played 3 games, C has played 2 games, and D has played 1 game. Then Wu Sai has played () games
This is as follows: 1. After 4 matches in a, it must be one match in each match, which means that one game has been played in the fifth match;
2. One game of d only means one match against a and one match with E;
3. If Party B has played three games, one of which is against a, the remaining two games can only be played with two of them, while Ding has only played one match with a, which means that the remaining two games are played against C and e respectively, then E has played another game;
4, the third match two games, just in front of a, B each game, with the fifth game
So in the end, there were two games for the fifth team, which were against a and B respectively
Four students, a, B, C and D, designed the following identification scheme for related substances: A: the use of CO2 gas can distinguish NaOH, Ca (OH) 2 and dilute hydrochloric acid solutions; B: if there is BaCl2 solution, there is a way to identify NaOH, Na2CO3, Na2SO4 and sulfuric acid; C: with phenolphthalein and BaCl2 solution, five solutions of hydrochloric acid, sulfuric acid, Na2CO3, NaOH and KNO3 can be identified; D: HCl, BaCl2, Na2CO3 and NaCl can be identified without any other reagent The following evaluation of these programs is correct () A. Only a works B. Only B and D are feasible C. Only B is not feasible D. All work
A: carbon dioxide is introduced into the three solutions respectively. If there is white precipitate, the calcium hydroxide solution is generated; if there is no obvious phenomenon, dilute hydrochloric acid and sodium hydroxide solution are not obvious, the white precipitate generated by the previous reaction is added to the two solutions that are not identified. If the precipitation disappears, it is dilute hydrochloric acid; if there is no obvious phenomenon, it is sodium hydroxide solution;
B: add a little of the four solutions to the excess barium chloride solution, and the original solution without obvious phenomenon is sodium hydroxide. Drop the three parts of the solution that produces precipitation into the precipitation. If the precipitation produces gas, the added solution is sulfuric acid, while the original solution producing the precipitation is sodium carbonate, the other original solution is sodium sulfate
C: add phenolphthalein solution to the five solutions respectively. If the solution turns red is sodium carbonate solution and sodium hydroxide solution, if there is no obvious change in dilute hydrochloric acid, dilute sulfuric acid and potassium nitrate solution, add barium chloride solution to the two solutions that have turned red. If there is precipitation, it is sodium carbonate solution; if there is no obvious change, it is sodium hydroxide solution; if there is no obvious change, three kinds of solutions are not identified If there is a white solution to produce dilute sulfuric acid, if there is no obvious change is dilute hydrochloric acid and potassium nitrate solution, respectively add the identified sodium carbonate solution to the two solutions that have not been identified. If there are bubbles, dilute hydrochloric acid emerges, if there is no obvious change, it is potassium nitrate solution;
D: mix the four solutions in pairs. Only dilute hydrochloric acid is produced by gas, and barium chloride solution is generated only by precipitation. Sodium carbonate solution is generated by precipitation and gas, and sodium chloride solution is generated without precipitation and gas. Therefore, it can be identified
Therefore, D is selected
How to distinguish (a, B, C, D...) Acid (methyl, ethylene, propylene, butyl...) ester
It depends mainly on the number of C, which is the same as that of methyl ethylene propylene butane
Four students, a, B, C and D, went to the forest to collect mushrooms. The integral part of the average number of mushrooms collected by each student was a two digit number with a ten digit number of three. It was also known that the number of mushrooms collected by a was 4 of B's 5. The quantity purchased by B is 3% of C 2 times. Ding picks 3 more mushrooms than Jia. So, Ding picks mushrooms______ One
If the number of mushrooms harvested in C is x, then 3 in B
2X, Jiacai 4
5×3
2x=6
5x, DingCai (6
5x + 3),
The number of mushrooms collected by four people was x + 3
2x+6
5x+6
5x+3＝49
10x+3，
Then according to the average number of mushrooms collected per person, the integer part is a two digit number with 10 digits of 3: 30 ≤ 1
4(49
10x+3)＜40，
117≤49
10x＜157，
one thousand one hundred and seventy
49≤x＜1570
49，
two thousand three hundred and forty-three
49≤x＜322
49，
49 again
10x must be an integer, X is a multiple of 10, so only x = 30,
Thus Ding Cai: 6
5x+3=6
5 × 30 + 3 = 36 + 3 = 39 (PCs.),
A: 39 mushrooms
So the answer is: 39
Four students of a, B, C and D stood in a row with Mr. Wang for photos. There were 120 kinds of standing methods. Why?
A total of five people, each person's position is different, the effect is not the same, this is a high school permutation problem
The total arrangement of five persons is: P (5,5) = 5 * 4 * 3 * 2 * 1 = 120 (species)
There are five possibilities for the first position. After the person is confirmed, there are four possibilities for four people in the second position. The following rules are the same
If the explanation is not clear, please ask
3. Arrange the natural numbers in the following form. The first line is 1,2,4,7,11 What is the number 100 in the first line? 1,2,4,7,11,…… 3,5,8,12,………… 6,9,13,……………… 10,14,…………………… 15,……………………………
So the first line 2-1 = 1 4-2 = 2 7-4 = 3 11-7 = 4
Starting with the second number, 2 = 1 + 1 4 = 1 + 1 + 2 7 = 1 + 1 + 2 + 3 11 = 1 + 1 + 2 + 3 + 4 ,
So the 100th is 1 + 1 + 2 + 3 + 4 + 5 + 6 + +98+99=4951
How to arrange all combinations of "1, 2, 3, 4, 5, 6" with excel?
Press Alt + F11 to open VBA editor, insert a module, put the following code in, pause the cursor in the middle of the code, press F5 to run. Public sub lwy() for a = 1 to 6For B = 1 to 6For C = 1 to 6For d = 1 to 6For e = 1 to 6For f = 1 to 6If a B and a C and a
RELATED INFORMATIONS
- 1. Observe the following group of numbers in regular order: - 1,2, - 3,4, - 5,6, - 7,8... Then what is the number 2006?
- 2. From one to six, every four numbers are combined. How many combinations are there How? Or what do you think? It's important to me
- 3. Add "+" or "- before the numbers 2, 3, 4, 5, 6, 7, 8, 9 to make the sum of them be - 10. How can you think of several ways?
- 4. A school selects three teachers from six teachers to support teaching in three remote areas at the same time, with one person in each place. Among them, a and B go differently, and a and C can only go together or not at the same time______ Species
- 5. Number permutation and combination 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 these numbers can be grouped into 11 groups. How many groups can we arrange
- 6. Take any two of the five numbers 1, 3, 5, 7, 9, and any two from the four numbers 0, 2, 4, 6 Take any two of the five numbers 1, 3, 5, 7, 9, and any two from the four numbers 0, 2, 4, 6 ask 1. How many four digits can be formed without repeating numbers? 2. How many even four digit numbers without repeating numbers can be formed?
- 7. Permutation and combination: take any three of the six numbers 1, 2, 3, 4, 5, 6 to form 3-digit even numbers which can not be repeated?
- 8. Five numbers 0,1,2,3,4 can be used to form three even numbers which are not allowed to repeat I know the answer is 30, and I want the process to be done in a combinatorial sequence
- 9. From 0 to 9, how many four digits can be divided by 5?
- 10. Arrange all six digits of two 3's and 4 0's in descending order
- 11. 1999 students in a row, from the front to the end of the line 1 to 3, and then from the end of the line to the front 1 to 4 1999 students in a row, from the front to the end of the line 1 to 3, and then from the end of the line to the front 1 to 4. How many of them reported 1 twice
- 12. There are 47 students in a row. 1 to 3 count off, and the last student reports how many students are there in this team? The students who report one step forward and stand in a line?
- 13. 55 students from class 5 (1) of a school formed a large circle. From the first student, the number was counted by 1, 2, 3 and 4. When the last student finished the report, the first student continued to report down according to the law. A total of 6 circles were reported. When the seventh circle began, the first student reported how many, there was a formula, and then, explain why, talk about analysis
- 14. In extracurricular activities, four people report the number. A says: 1. B says 2, C says 3, and Ding says 4. In this way, the total number of people reported is more than money. Ask 34 who reported it. 71 who reported it
- 15. -3 / 4, 5 / 7, - 10 / 9, 17 / 13, - 33 / 16 to find the law, what is the number 2012
- 16. Look at the following list: half, one sixth, one twelfth, one twentieth Please find out the rule of arrangement and press here Fill in the blank regularly The fifth number is—— The number in 2011 is——
- 17. The number of columns arranged according to the regulations is 2, 3, 10, 15, 26 and 35. What is the seventh number? If the answer is right, a reward will be offered!
- 18. The number of a column: 1,3 + 5,7 + 9 + 11,13 + 15 + 19,12 + 23 + 25 + 27 + 29?
- 19. There are 120 five digits made up of 1, 2, 3, 4 and 5. Put these five digits in order from small to large, and the 95th number is______ .
- 20. How many five digits can you make up with 12345?