Answer: twice. Divide 9 packets of salt into 3 portions, each with 3 packets, and put 2 packets at both ends of the balance, so there are two situations:
(1) The balance is unbalanced. This shows that fake salt must be in the three bags at the drooping end of the balance.
(2) balance. This means that fake salt is in the third part (three bags not on the scale)
If you have found fake salt in San Bao, you can distribute the San Bao according to the above method, weigh it again and find fake salt.
A math problem! Urgent! One: 5 × (5-5 ÷5÷ 5)
2: 5 × (5-(5÷5 ÷ 5))
Three: (5-5÷5 ÷ 5) × 5
Four: (5-(5÷5 ÷ 5)) × 5
Urgent, the formula on a math problem is = a 2m 2+b 2n 2+a 2n 2+b 2m 2+c 2m 2+c 2n 2.
=(a^2+b^2+c^2)*m^2+(a^2+b^2+c^2)*n^2
=(a^2+b^2+c^2)*(m^2+n^2)
Solve a math problem 2, 5, 26, 63, 82, ()
3 1 42 c 126d 167
The answer is 3 1
Solve a math problem 89* 1+275=364.
Thank you for solving a math problem! . . .
. . .
. . .
All right, that's it. You will have nine lines. I did this problem in the sixth grade.
Need a math problem urgently! A Dai logs on to Baidu every 2 days, A Xiong logs on to Baidu every 3 days and A Sha logs on to Baidu every 7 days. If they log in to Baidu at the same time on June 65438+1 October1,when will they log in at the same time next time?
Find four math puzzles (grade five), including the answer 1. There are a number of parts. Master Zhang finished 2 hours ahead of schedule and 4 hours later than the stipulated time. If two people work together for three hours, and Li Shifu finishes the rest by himself, it will be finished within the stipulated time. How many hours will it take if two people cooperate to complete this batch of parts?
Solution 1 (suitable for olympiad):
According to the meaning of the question, it takes four hours for a person to work, and three hours for Master Zhang to help is just enough. That is to say, three hours for Master Zhang is equal to four hours. That is to say, it takes three-quarters of Li's time to finish the same thing, but their time difference is six hours, so Li's time to finish is 6/( 1-3/4) = 24 hours, Zhang.
Solution 2:
Let the specified time be x, 3 * (1/(x-2)+1(x+4))+(x-3)/(x+4) =1.
The solution is x=20.
So the cooperation time of two people is1/(1(x-2)+1(x+4)) = 72/7 hours.
2. A class of 35 people signed up for this year's Olympic Mathematics remedial class. There are 23 boys in this class. How many more girls are enrolled in this class this year than boys who are not enrolled?
If the number of boys who didn't sign up is A, then the number of boys who signed up for the competition is 23-a, and the number of girls who signed up for the competition is 35-(23-a)= 12+a, so there are more girls who signed up for the competition than boys who didn't sign up for the competition 12.
3. A group of students planted trees. Each of them planted 6 trees, and there were 4 trees left. If three of them planted five trees each and no one else planted seven trees each, how many students are there in this group? How many trees have been planted?
Settings; There are x students.
6X+4=3*5+7(X-3)
6X+4=7X-6
-X=- 10
X= 10
Answer; There are 10 students.
6 * 10+4 = 64 (tree)
Answer; * * * planted 64 trees.
The RMB * * * in 4.2 yuan and 5 yuan is RMB 1 15. If RMB is replaced by 2 yuan and 5 yuan, it will be RMB 15 1 yuan. How much RMB are there for two yuan and five yuan?
Settings; 2 yuan RMB X
( 1 15-2X)÷5 * 2+5X = 15 1
230-4X+25X=755
2 1X=525
X=25
Answer; 2 yuan RMB 25 yuan.
(115-2 * 25) ÷ 5 =15 (Zhang)
Answer; 5 yuan RMB 15.
Ask a math problem: let the second pile of sand weigh x kilograms.
The first pile of sand:
x+37 = 4x + 4
3x=33
x= 1 1
So the second pile of sand weighs 1 1kg.
The first pile of sand weighs 48 kilograms.
I want 20 math problems 1. There are a number of parts. Master Zhang finished these parts two hours ahead of schedule and four hours behind schedule. If two people work together for three hours, and Li Shifu finishes the rest alone, it can be finished in time. How many hours will it take if two people cooperate to complete this batch of parts?
Solution 1 (suitable for olympiad):
According to the meaning of the question, it takes four hours for a person to work, and three hours for Master Zhang to help is just enough. That is to say, three hours for Master Zhang is equal to four hours. That is to say, it takes three-quarters of Li's time to finish the same thing, but their time difference is six hours, so Li's time to finish is 6/( 1-3/4) = 24 hours, Zhang.
Solution 2:
Let the specified time be x, 3 * (1/(x-2)+1(x+4))+(x-3)/(x+4) =1.
The solution is x=20.
So the cooperation time of two people is1/(1(x-2)+1(x+4)) = 72/7 hours.
2. A class of 35 people signed up for this year's Olympic Mathematics remedial class. There are 23 boys in this class. How many more girls are enrolled in this class this year than boys who are not enrolled?
If the number of boys who didn't sign up is A, then the number of boys who signed up for the competition is 23-a, and the number of girls who signed up for the competition is 35-(23-a)= 12+a, so there are more girls who signed up for the competition than boys who didn't sign up for the competition 12.
3. A group of students planted trees. Each of them planted 6 trees, and there were 4 trees left. If three of them planted five trees each and no one else planted seven trees each, how many students are there in this group? How many trees have been planted?
Settings; There are x students.
6X+4=3*5+7(X-3)
6X+4=7X-6
-X=- 10
X= 10
Answer; There are 10 students.
6 * 10+4 = 64 (tree)
Answer; * * * planted 64 trees.
The RMB * * * in 4.2 yuan and 5 yuan is RMB 1 15. If RMB is replaced by 2 yuan and 5 yuan, it will be RMB 15 1 yuan. How much RMB are there for two yuan and five yuan?
Settings; 2 yuan RMB X
( 1 15-2X)÷5 * 2+5X = 15 1
230-4X+25X=755
2 1X=525
X=25
Answer; 2 yuan RMB 25 yuan.
(115-2 * 25) ÷ 5 =15 (Zhang)
Answer; 5 yuan RMB 15.
5.5 According to the figure of 1-5, the prisoners used sacks containing 100 mung beans to catch mung beans. It is stipulated that everyone should catch at least one, and those who catch at most and at least will be executed, and they can't communicate with each other, but they can find out the remaining number of beans when catching. Ask them who has the best chance of survival.
Tip:
1, are very smart people.
Their principle is to save people first, and then kill more people.
3, 100 don't have to finish it all.
4. If there is any duplication, it will be regarded as the largest or smallest and executed together.