2010 8th Grade Happy Winter Break Answers 19 to 50

11. It is known that a railway bridge is 1000 meters long, and an existing train passes through the bridge, and it is measured that the train takes 1 minute from the beginning of the bridge to the end of the bridge, and the time for the whole train to be completely on the bridge is 40 seconds, and the speed of the train and the length of the train are obtained.

Let the speed of the train be a meter per second and the body length be b meters.

1 minute = 60 seconds.

60a=1000+b

40a=1000-b

100a=2000

a = 20 m sec.

b=60x20-1000

b = 200 meters.

The length of the body is 200 meters. The speed of the vehicle is 20 meters per second.

12. A and B run on the ring road at the same speed, if they start at the same time and in the same place. Walk in the opposite direction, meeting every 2 minutes; If you are traveling in the same direction, meet every 6 minutes. It is known that A runs faster than B, how many laps does A and B run per minute?

Solution: Let A run x laps per minute and B run y laps per minute. According to the question of the equation, the following is obtained

2x+2y=1

6x-6y=1

x=1 3 , y=1 6

A: A runs 1 3 laps per minute, B runs 1 6 laps per minute.

13. There are 100 pieces of five jiao, one yuan, and two yuan, totaling 100 yuan. Among them, the total of five jiao and two yuan is 75 yuan, how many pieces of each type of yuan?

Solution: The pentagram has a sheet, the one yuan has a sheet, and the binary one has 100-a-b sheets.

According to the title. 2) Substitution (1).

b = 100-75 = 25 sheets.

Substitution (2) 75 = a = 50

So there are 50 pentagrams, 25 for one, and 25 for binary.

14. A and B each brought some money, and if A gets half of B's money, then A has a total of 50If B gets two-thirds of all of A's money, then B also has a total of 50 money. Q: How much money did A and B bring?

Solution: Set A with money A yuan, B with money B yuan.

a+1/2b=50（1）

b+2/3a=50（2）

Simplification 2a+b = 100(3).

3b+2a=150（4）

2b = 50b = 25 yuan.

a=50-25 2=yuan.

A brought 25 yuan, and B brought 25 yuan.

15. A and B have deposited a total of a certain amount of yuan in the bank, and it is known that one-fourth of A's deposit is equal to one-fifth of B's deposit, and it is known that B has deposited 24 yuan more than A, how much is A and B?

Solution: Let A have a yuan and B have B yuan.

1/4a=1/5b

b-a=24

The solution is a=96

b = 12016, A and B do a total of one job, A first did 5 days B did 20 days to finish, if A first 20 days B did 8 days to finish. So how long does it take for A and B to do it together.

A's work efficiency is A, and B's work efficiency is B

5a+20b=1（1）

20a+8b=1（2）

72b=3b=1/24

5a=1-20/24

5a=1/6

a=1/30

It takes 1 (1 24 + 1 30) = 24 30 54 = 40 3 days.

Which publisher You Ball Ball I add you.

Where are you? What version of the textbook?

Happy winter vacation.

The annual winter vacation is coming again, everyone must know that there is one of the most solemn festivals in our country during the winter vacation - the Spring Festival, during the Spring Festival, I have many happy things: fireworks, New Year's greetings, red envelopes, etc., among which the happiest thing for me is to set off fireworks.

On the morning of the thirtieth day of the Chinese New Year's Eve, my father bought back a lot of fireworks, with a complete variety, including cupolas, kaleidoscopes, magic bullets, dragon buds, fairy scattered flowers, dreams come true, and great fortune, among which my favorite is fairy scattered flowers.

At dinner, I couldn't wait to set off the fireworks, and my mother said, "I'll put them off after dinner." When I heard this, I devoured it, and before the dish was finished, I ate it.

After a while, my mother announced, "Now our whole family is going downstairs to set off fireworks!" "I scrambled downstairs to get fireworks in the garage, and I was sweating profusely.

I first took out the "magic bullet" and asked my father to help me light it, I closed my eyes and raised my hands in the air, only to hear a "squeak", I hurriedly opened my eyes, but the fireworks had flown away without a trace. At this time, I only heard a "whew", which frightened me and hurriedly covered my ears, I thought: This is really a tiger roaring and a lion roaring!

It turned out that my father put up the "dragon chanting flower thunder", although the tiger roared and the lion roared, but after a while, it was colorful and autumn rain.

The fairy scatters flowers, but it looks good! At first, I lit the fuse, and suddenly a beam of golden light flew into the sky, and suddenly opened, turning into many colorful dots, and after a while, those dots turned into small golden flowers, like a child's smile, which was really refreshing and beautiful.

Then, I put "dreams come true", after lighting the fuse, a small fireball flew into the air and gradually became larger, spraying ** flames, colorful, the flames of the spray were big and small, fast and slow, gathering and scattering, as if the Yangtze River that would breathe flames, flowing endlessly. In this way, our family was very busy throughout Chinese New Year's Eve!

How can there be a banquet in the world, time passed minute by minute, and the fireworks were over, but my heart was like fireworks, and I was immersed in the world ......of fireworks for a long time

The Spring Festival is coming, happy events, on the first day of the Lunar New Year, I went to my relatives' house to pay New Year's greetings, every time I went to a house, I got a red envelope, tell you, I took a total of about 4,000 yuan, plus my usual pocket money can be really a lot, my mother said: "When I go to college." I nodded happily.

There are so many happy things in the Spring Festival, think about it, I live so happily, in the future, I must study hard and create a better tomorrow with my own hands.

You're still done.,In the right answer.,Don't copy it directly.,Otherwise,There's no effect at all.,I'm about to go to the third year of junior high school to take the high school entrance examination.,Homework can't be taken lightly.。

22. Red Star Manufacturing Factory is ready to recruit a total of 150 workers A and B, the monthly salary of each worker in type A is 600 yuan, the monthly salary of each worker in type B is 1,000 yuan, and the total monthly salary of workers in the two types of work is 100,000 yuan.

Solution: Set up the enrollment of type A worker A, and type B 150-a.

According to the title. 600a+1000（150-a）=100000

6a+1500-10a=1000

4a=500

a=125 people.

125 people are enrolled in type A, and 150-125 = 25 people in type B.

Or: Set up enrollment of A and B.

a+b=150

600a+1000b=100000

The solution is a=125

b = 2523, there is a two-digit number, divide it by the sum of its numbers, the quotient is 5, and after exchanging two digits, divide it by the difference between two times the single digit of the original number and ten digits, then its quotient is 9, find this two-digit number.

Solution: Let this two-digit number be 10a+b

According to the title. 10a+b=（a+b）×5

10b+a=（2b-a）×9

Simplification 5a = 4b

a=4b/5

b=0，1，2，3，……9

So only b=5 and a=4 fit the topic.

This two-digit number is 45

24. The circular track of a stadium is 400 meters long, and A and B practice long-distance running and cycling at a certain speed respectively. If they go in reverse, then they meet every 30 seconds. If they are traveling in the same direction, then B catches up with A every 80 seconds.

What is the speed of A and B?

Solution: Let the speed of A be a meter second and the speed of B b meter second.

According to the title. a+b）×30=400

b-a）×80=400

Simplification a+b=40 3(1).

b-a=5（2）

2b=55/3

b = 55 6 m sec.

2a=25/3

a=25 6 m sec.

The speed of A is 25 6 meters per second, which is 250 meters per minute.

B's velocity is 55 6 meters per second, which is 550 meters per minute.

25. From city A to city B, the waterway is nearly 40 kilometers closer than the land route, at 11 o'clock in the morning, a steamer travels from city A to city B at a speed of 24 kilometers per hour, and at 2 o'clock in the afternoon, a car travels from city A to city B at a speed of 40 kilometers per hour, and the ship and car arrive at city B at the same time.

Solution: Set up a kilometer by water and kilometer B by land.

a+40=b（1）

a/24-3=b/40（2）

1) Substitution (2).

a/24-3=（a+40）/40

1/60a=4

a = 240 km.

b = 240 + 40 = 280 km.

240 km by water and 280 km by land.

Note: There is a difference of 3 hours between 11 a.m. and 2 p.m.

What region are you in? Winter vacation homework is not the same everywhere.