Olympiad math problems in the summer vacation homework of the fifth grade, and a few questions in th

If there are 4 rows, each row will be x people, and when there are 5 rows, each row will be y people, 4x+1=5y-14x+2=5y

The above equation satisfies 45+1<5y<60+1

y can only be 10, 11, 12

When only y=10 above, x is an integer 12, so there are 49 students in this class.

According to the first condition, it is known that this number is a multiple of 4 after subtracting one.

In 45-60, there are 45 49 53 57 four.

The second condition knows that this number is a multiple of 5 after adding one, and the end is either 9 or 0, so the number obtained by combining the two conditions is 49

Between 45 and 60, 48 divided by 4 is exactly 50 divided by 5 is exactly divided by four more by one divided by five less one, so it's 49

There are a total of x people.

then both (x+1) 5 and (x-1) 4 are divisible, because 45 60, so.

x+1=45 or 50 or 55 or 60, then x=44 or 49 or 54 or 59x-1=44 or 48 or 52 or 56, then x=45 or 49 or 53 or 57 finally meets the condition only x=49

49 people, I also don't know how to do this problem, I only know the answer.

There are x people in this class.

45(x-1)/5

x,(x+1) 4,(x-1) 5 are integers.

x=49

(1 person.)

2 (80-75) = 6 minutes.

80 + 75) * 6 = 930 meters.

3. Keg: capacity 10 liters, 100 yuan 1 barrel. 100 10 = 10 yuan per liter drum: capacity 15 liters, 140 yuan 1 barrel. 140 yuan 15 yuan per liter 10 yuan.

The best way to save money is to buy paint in large barrels.

4. Kilograms. 5, Yuan 6, (10-1*2)*(7-1*2)*1=40 cubic decimeters +7=12

78 12 = people, off topic.

8. Suppose that 10 are all big boats, which can sit 6*10=60 people, 60-44=16 more people, and each small boat counts 6-4=2 more people, so there are 16 2=8 small boats, 10-8=2 large boats.

2 = 36 yuan.

60-36=24 yuan.

$5 of 24 (5-2) = 8 sheets.

18-8 = 10 sheets for 2 yuan.

Rice. 11. Speed and 320 2=160

The speed of car A is 160*3 8=60

The speed of car B is 160*5 8=100

When we meet, car A travels less than car B (100-60) * 2 = 80 kilometers to adopt, I am very hard.

1.Class 6 (1) originally planned to participate in the computer competition, but later increased by 2, so that the number of participants in the competition accounted for one-sixth of the class size, how many students from Class 6 (1) participated in this computer competition?

Solution: The participants in this computer competition have a total of:

8 people. 2.Xiao Ming and Xiao Liang set off from each other at the same time, Xiao Ming walked 80 meters per minute, Xiao Liang walked 75 meters per minute, and the two met at a distance of 15 meters from the midpoint. How many meters are the distance between A and B?

Solution: A and B are far apart:

930 meters. 3.There is a certain coating, divided into large, small barrel two specifications of packaging, how to buy different packaging of paint to save the most money?[Actually, I don't understand this question].

1) Keg: capacity 10 liters, 100 yuan 1 barrel.

Large barrel: capacity 15 liters, 140 yuan for 1 barrel.

Solution: According to the amount required, you should try to save money by buying large barrel packaging.

Unit price of large barrels: 140 15 = yuan liters.

The unit price of a keg: 100 10 = 10 yuan liters.

4.There were 40 students in Year 5 Class 1, and their average weight was kilograms, and after one student was transferred, the average weight of the whole class was 39 kilograms. How many kilograms did the student who transferred away weigh?

Solution: The weight of the student who transferred away was:

43kg of bream is equal to the ** of 5 crucian carp, and each bream is more expensive than each crucian carp. How much is each crucian carp?

Solution: Every crucian carp**:

Solution: The volume of this box is:

10-2)*(7-2)*1=40 cubic decimeters.

7.The average number of people in the two workshops is 78, and the ratio of the number of people in the two workshops is 5:7

Solution: Workshop A has:

78*2*5 (5+7)=65 people.

Workshop B has: 78*2*7 (5+7)=91 people.

8.There were 44 students rowing in a total of 10 boats, with 6 people in each large boat and 4 people in each small boat. How many big boats and small boats are there? [I know the answer, I don't know how to write the equation].

Solution: There are a number of small boats:

8 only large ships number:

10-8=2 pcs.

9.There are 18 bills of 2 yuan and 5 yuan in Xiaoxiao's piggy bank, totaling 60 yuan. How many $2 and $5 notes are there? [I also know the answer, I don't know how to write the equation].

Solution: 2 yuan has:

10 sheets. 5 yuan has:

18-10=8 sheets.

10.The two teams worked together to dig a 520-metre tunnel, which took 20 days to complete. How many meters does engineering team A dig every day, how many meters does engineering team B dig every day?

Solution: Engineering team B excavates every day

m days. The two places are 320 kilometers apart, A and B two cars are from A, B at the same time in the opposite direction, 2 hours to meet, it is known that the speed of A and B is 3:5, when they meet, car A is less than car B how many kilometers?

Solution: Car A travels less than car B when they meet:

80 km.

Person.

Rice. 3. The small barrel is 10 yuan per liter, and the large barrel is 140 15 yuan per liter, so the small barrel is relatively cheap.

Kilogram. 5. Yuan.

cubic decimeters. 7. There are 65 people in workshop A and 91 people in workshop B.

8. Let the big ship x and the small boat 10-x, the equation: 6x+4(10-x)=44, and the solution x=2, then there are 2 large ships and 8 small boats.

9. The method is the same as above.

10, m. Kilometer.

4. 40 kg) 39 (40-1) = 1521 (kg) 1564-1521 = 43 (kg).

9. 2 18 = 36 (yuan) 60-36 = 24 (yuan) 5 yuan: 24 (5-2) = 8 (zhang) 2 yuan: 18-8 = 10 (zhang).

10. 520 20 = 26 (m) m).

1/4 plus 2/3 equals 11/12

There is only one way to fill in.

If the two denominators are different denominators, and the multiplication of the different denominators is 12, there is only 3 times 4, or 2 times 6, or 1 times 12

But to be equal to 11/12, less than 1, then 1 times 12, the common divisor of 2 and 6 is 2, and the denominator will not get 12, so it is also discharged.

Finally, choose 1/4 plus 2/3

Li Lin was going to bring back a few greeting cards to his friend. He learned that each greeting card was worth yuan, so he came to the store with the money he could buy 12 greeting cards, and after bargaining, the cards were cheaper each one. Please help Li Lin calculate how many greeting cards he can buy with the money he brings now?

Take an approximate value according to the actual situation).

Answer: Zhang. A: You can buy 19 sheets.

Dear: Hello

Answer: 1. Idioms that begin with odd numbers: 1) single-mindedness, 2) unstoppable, 3) half-hearted, 4) colorful, 5) colorful, 6) varied, 7) seven up and eight down, 8) seven mouths and eight tongues, 9) nine cows and one hair, 10) nine deaths and one life.

Idioms that begin with an even number: 1) two words are not spoken, 2) two dragons play with pearls, 3) accessible in all directions, 4) embattled, 5) surrounded by all directions, 6) four seas are home, 7) six relatives do not recognize, 8) six gods have no owner, 9) eight sides are exquisite, 10) perfect.

2. Find a calendar card for this year, and use a cuboid shaped like [] to frame the number of dates in the calendar, and box three numbers each time, how many different sums can be framed? How many ways are there to frame the sum of three numbers that are 33? : 49 different sums can be framed. There is only 1 type of boxing.

3. There are 20 people in the song and dance team, there is an emergency performance, and the captain plays ** in the way of **, one pass ** for one minute, how long does it take at least? : Minimum 5 minutes.

4. There are ten piles of jelly, each pile of ten bags, and the quality of each bag in one pile is less, how to find out the defective products at one time? : Yes (5,5) points, a total of 3 times.

1.。2., minutes, call 1 first, 2 tell 3, 4 tell 7, 8 tell 15, and then 5 tell respectively.

4.Put the two bags on both sides of the scale, and the clean is the defective product.

Solution: There are x children, Y pieces of candy.

3x+3=y

5x-1=y

The solution yields x=2 y=9

A: There are 2 children and 9 pieces of candy.

Profit and loss issues.

3+1) (5-3) = 2 people.

2*3+3=9 pieces of sugar.

The sum of profit + loss divided by the difference between the two distributions (formula).

There are a few children; (1+3) (5 3) 2 (pcs).

There are two ways to find the sugar number; 1,2 3 3 = 9 (block).

2, 2 5 1 = 9 (block).

Solve with equations: If there are children x people, there will be sugars (3x+3).

5x-1=3x+3

x=2 has 2 children and 9 candies.

There are x people.

3x+3=5x-1

x=23*2+3=9

9 pieces of sugar for two people.

There are x number of children.

3x+3=5x-1

x=2 so there are 2 children.

Sugar has 5*2-1=9 pieces.

It can be solved with equations.

Let the child be x and the sugar be y.

The solution yields y=9, x=2

The number of students in this class is 40, and the number of people who have subscribed to the newspaper is 47.

So 47-40 = people subscribe to two kinds of newspapers.

1.Write words according to their meaning.

1) I was very scared. ( Frightened )

2) Describe the situation as extremely critical (at stake).

3) Forge ahead bravely, regardless of the danger to life. (4) The appearance of the water is magnificent. (Magnificent waves).

29 years old first step (42-3) 3=13 (years).

Step 2 3+13=16 (years).

Step 3 42-13=29 (years) Analysis: The first step (when the teacher is 42 years old, 42 years old contains a 3-year-old and three age differences, therefore, as long as you subtract 3 years old from 42 years old, there are three age differences, divide by 3, you can get the age difference between Xiao Ming and Teacher Liu) Step 2 (know the age difference, it was said earlier that when Teacher Liu is as old as Xiao Ming, Xiao Ming is only 3 years old, the teacher is 13 years older than Xiao Ming, 3 plus 13 will get that Xiao Ming is 16 years old) Step 3 (Xiao Ming is 16 years old this year, 16 plus 13 to get Mr. Liu 29 years old) Draw the line diagram yourself to understand.

42-3=39

Ms. Liu is 29 years old.

Xiaole is 16 years old.

Children, study hard, don't rely on answers, and you will be happy if you make it yourself.

It's all set!

1. There are 40 students in a class, of which 15 participate in the mathematics group, 18 in the model aircraft group, and 10 in both groups. So how many people don't participate in both groups?

2. After the results of a class of 45 students took the final exam, 10 students got full marks in mathematics, 3 students got full marks in mathematics and Chinese, and 29 students did not get full marks in these two subjects. So how many people got a perfect score in Chinese?

The students stood in a line facing the teacher. The teacher first asks everyone to press 1, 2, 3 ,...... from left to right49,50 in turn; Then ask the student who reported a multiple of 4 to turn back, and then let the student who reported a multiple of 6 turn backward. Q:

How many students are there for teachers now?

4. At the amusement fair, 100 students drew lottery tickets with labels from 1 to 100. The rules for awarding prizes according to the ticket tag number are as follows: (1) If the tag number is a multiple of 2, 2 pencils will be awarded; (2) If the label number is a multiple of 3, 3 pencils will be awarded; (3) The label number is both a multiple of 2 and a multiple of 3 to claim the award repeatedly; (4) 1 pencil will be awarded for other label numbers.

So how many prize pencils are there for this event?

5. There is a rope with a length of 180 cm, starting from one end every 3 cm to make a mark, every 4 cm also to make a mark, and then cut the marked place. Q: How many pieces of rope have been cut?

Answer to 5th grade question 3.

1. Because 10 people and 2 groups participated, 5 people only participated in mathematics, 8 people only participated in model aircraft, plus those 10 people were 23 people, 40-23 = 17, 17 people who did not participate in 2 groups.

2. In the same way, there are 10 people with a full score in mathematics and 3 people with a full score in 2 subjects, so there are only 7 people with a full score in mathematics, 45-7-29 = 9, this is the person with a full score in Chinese (if it is only a full score in Chinese, you need to subtract 3).

3,50 4 round 12,50 6 round 8, but note that the multiple of 4 may be a multiple of 6, so you also need to calculate the common multiple of 4 and 6, there is 50 12 (the least common multiple of 4 and 6) = 4 (rounded), so, it should be 50-12-8 + 4 = 34

4,100 2=50,100 3=33 (rounded), or calculate the common multiple of 2 and 3 100 6=16 (rounded), and then find the number of numbers that are not divisible by 2 and not divisible by 3 100-50-33+16=28, so prepare a pencil for 50x2+33x3+28=227

5,180 3=60,180 4=45, but maybe 2 dashes are drawn together, that is, to calculate their common multiples, 180 3 4=15, so it should be 60+45-15=90