A 5th grade math problem easy is worth 50 points

60*2 (book).

Zu Chongzhi's outstanding achievement in mathematics is about the calculation of pi Before the Qin and Han dynasties, people to"Trail three times a week"As pi, this is"Ancient rate"Later, it was found that the error of the paleorate was too large, and the pi should be"The circle diameter is more than three days", but how much is left, opinions differ Until the Three Kingdoms period, Liu Hui proposed a scientific method for calculating pi"Circumcision", use the circumference of the circle inscribed regular polygon to approximate the circumference of the circle Liu Hui calculates that the circle is inscribed with 96 polygons, and obtains =, and points out that the more sides of the inscribed regular polygon, the more accurate the value obtained Zu Chongzhi on the basis of the achievements of his predecessors, after hard work, repeated calculations, found In between and and obtained the approximate value in the form of fractions, taken as the approximate rate , taken as the dense rate, where the six decimal places are taken, it is the fraction of the closest value of the numerator denominator within 1000 What method did Zu Chongzhi use to get this result, Now there is no way to examine if it is assumed that he will press Liu Hui's"Circumcision"If you want to find this method, you have to calculate that the circle is connected with 16,384 polygons, which requires a lot of time and labor! It can be seen that his tenacious perseverance and intelligence in his scholarship are admirable Zu Chongzhi's calculation of the dense rate, it has been more than a thousand years since foreign mathematicians achieved the same result In order to commemorate Zu Chongzhi's outstanding contributions, some foreign historians of mathematics have suggested that = be called"Ancestral rate"．

60 times 2 divided by (multiplied by this).

At the age of 21, De Moivre was already teaching mathematics for a living, and he was convinced that he was fully proficient in the subject. By chance, he was a guest at a duke's house, and Newton (Newton) sent his "Principia", he flipped through it, and was surprised to find that mathematics was so profound and so beautiful. In this way, he bought the book, although he had to tear off the pages so that he could carry it in his pocket and study it at his leisure.

De Moivre has a theorem that seems to be in our middle school textbooks, which says that it is a plural to the nth power.

Think of the van as.

Big trucks are. The car is.

Large trucks are small cars.

One in eighteen.

Set up a large truck.

1*3=3。So there are three vans.

3*6=18。There are 18 cars.

1 is 1 18 of 18, and the wagon is 18 of the small axle car.

This question was answered by my son.

Set the house x meters away from the school, x-120 = 70 (x 90 + 120 90) solves x = 960 meters, (960-120) 70 = 12, so they meet after 12 minutes.

Solution: Suppose the brother and sister meet in x minutes.

90x-70x=120×2

20x=240

x = 12 assuming their home is x meters from the school.

x+120）÷90=（x-120）÷707×（x+120）=9（x-120）

7x+840=9x-1080

2x=840+1080

2x=1920

x=960A: The brother and sister met 12 minutes later, and their home was 960 meters away from the school.

Solution: Let's meet in x minutes.

90x-70x=120*2

20x=240

x=240/20

x=12A: Meet after 12 minutes.

70*12=840 (m).

840 + 120 = 960 (meters).

A: Their home is 960 meters away from the school.

Hopefully).

How does it look like they are ......... 100-meter race

It is easy to see that the brother is 20 meters faster than the younger sister, and the older brother walks 120 2 240 meters more than the younger sister, so the time for the brother and sister to meet is 240 20 12 minutes, and their house is 70 12 120 960 meters from the school.

If you have to use an equation, then if the brother and sister meet after walking for x minutes, then 90x 120 2 70x, the solution is x 12 minutes.

My sister is 120 meters from the school, so the home is 70 12 120 960 meters from the school.

Set the distance to Y meters, meet in x minutes.

Then y=70x+120=90x-120

So: x = 12 minutes.

y = 960 meters.

120*2 (90-70)=12 (minutes).

70*12+120=960 (m).

A: The siblings met 12 minutes later, and their home is 960 meters away from the school.

Let the distance x, equal according to the time: x-120 70 = x + 120 90, x = 960, time 12 minutes.

1. Each boy can get 1 or 3 pieces of bread.

Each girl can get 2 7 pies.

1 3>2 7 Therefore the boys have a great share.

2. One loaf of bread is divided into 3 boys, that is, 2 loaves can be divided among 6 boys and 2 loaves can be divided among 7 girls.

So 7 boys get more bread than 7 girls.

So the boys got a lot of it.

According to the title, it is to find the greatest common multiple of 6 and 8 within 100.

6x8=48，48x2=96

96 is the greatest common multiple of 6 and 8 within 100.

A: They are up to 96 people.

Least common multiple of 6 and 8: 24

They have the most: 24 4 96 (people).

The total area of the two sides of the cabinet is calculated: (sq.m.)

The top surface area is square meters.

The back area is in square meters.

The two small doors at the top are almost one-third the height of the main cabinet from the picture, so the height of the cabinet door should be meters.

The door area is square meters.

Then the total surface species to be brushed should be square meters.

According to 1 square meter, 5 grams of paint are counted as grams.

47-2=45

45 and 36 are multiples of the number of people, and the common factor of 45 and 36 is 3 3, so there are a maximum of 3 3 = 9 students in this group.

Each student was given water candy (47-2) 9=5 pieces.

Chocolate (39-3) 9 = 4 pieces.

47-2 = 45 (block) 39-3 = 36 (block) The greatest common factor for 45 and 36 is 9Water candy: 46 9 = 5 (blocks).

Chocolate: 36 9 = 4 (blocks) Answer: There are a maximum of 9 students in this group; Each student was given 5 pieces of fruit candy and 4 pieces of chocolate.

You draw a line on the left to make the polygon a rectangle.

To find the area of this triangle, we can get the s rectangle -s triangle x+y=15

x +z = 81 ( for power).

y^+z^=144

Find z, where z is the height of the triangle.

15*z2=area of the triangle.

Know the rest.

1 (1 7 1 9) 63 16 4 days (days cannot be rounded).

Your algorithm is a coincidence, and it's definitely not right. If the question is changed to 5 days and 11 days, your answer is still 4 days, according to my method, it is not 4 days, but days.

Because abcd is square, ab=4, therefore, ac=4 root 2

oc = 2 root 2

Therefore, s yin = s garden - s positive.

2 root 2) 4 4

Sun Long, a fifth-grade student, replied.

Solution: Let the denominator be x and the numerator y. i.e. y x

y/x+1/x=1①，y/x-1/x=7/8②①+=2(y/x)=15/8

y/x=15/16

So this score is 15 16

The area of a rectangle minus the area of a triangle.

The following sqrt(x) represents the root number x

p=(9+12+15)/2=18

s=20*15-sqrt(18*9*6*3)=246 with an area of 246

21-12 = 9.

12 divided by 2 = 6.

There are 9 + 6 = 15 seats in 1 3 on the bus.

Then there are 15 * 3 = 45 seats in the car.

Passengers are 45 + 12 divided by 2 = 61 passengers.

1. A barrel of oil is used up in two parts, and one-third of it is used up the first time.

2. Two-thirds of the kilograms were used for the second time, and the barrel of oil totaled (2) kilograms.

2. Pour 60 liters of water into a cube container with an edge length of 5 decimeters, and the water height ( ) cm.

3. The surface area of the cube is 384 square centimeters, the volume is 512 square centimeters, and the sum of the edge lengths of the cube is (96cm).

4. A rope is 256 cm long, wraps around a cube with a volume of 512 cubic centimeters, and can be wound up to (8) times.

5. There is a batch of rice in the warehouse, 5/24 of the total is 240 kg for the first time, 2/3 of the total is taken out for the second time, and (768) kg is taken out for the second time.

8.1 ton = 1 cubic meter.

Solution: Set the water depth to x meters.

18×8x=720

x=5A: The water depth is 5 meters.

9.About = A: Save 10,000 yuan than the original plan, saved.

10.30 42% = kilograms).

kilogram) A: It can be formulated into an alcohol solution containing 15% alcohol 84 kg.

11.140 (1-1 4-1 3) = 336 (km) Answer: A and B are 336 km apart.

12.(25-16) 5%=180 (person), 180-9=171(person).

325-171=154.(person).

A: There are 171 boys and 154 girls in the primary school.

3 (1-2 3) = 2 (kg).

5 5 = decimeter) = 24 (centimeter).

6 = 64 (square centimeters) 64 = 8 8, 8 12 = 96 (centimeters).

8 8 8 8 4 = 32 256 32 = 8 (circle).

5 24 = 1152 (kg) 1152 2 3 = 768 (kg).

8. Solution: Set the water depth x meters. 18×8x=1×720 x=5

42% 15% = 84 (kg).

(1-1 4-1 3) = 336 (km).

16 = 9 (person) Original boy: 9 5% = 180 (person) Current boy: 180 (1-5%) = 171 (person) Now girl: 325-171 = 154 (person).

1.2 3 (1-2 3) = 2 (kg) 2. 60 (5x5) = decimeter) = 24 cm.

3。384 6 = 64 (square centimeters) Indicates that the edge length is 8 cm, and the sum of the edge lengths: indicates that the edge length is 8x12 = 96 (cm).

4. The volume is 512 cubic centimeters, which means that the edge length is 8 centimeters, a circle is 4x8 = 32 centimeters, and the number of circles: 256 32 (circles).

5。Total: 240 5 24 = 1152 (kg) Second take-out: 1152x2 3 = 768 kg).

6， （60x20/100）÷75/100=16

8, 720 18 8=5 (m).

10.Find out how much pure alcohol there is: 30 x 42% = kg).

How many kilograms of 15% alcohol solution is found? : kg).

11.Remaining fractions: (1 1 4 - 1 3) = 5 12 Total distance: 140 5 12 = 336 (km).

12。Number of male students transferred: 25-16 = 9 (people).

Original boys: 9 5% = 180 (people).

Current boys: 180-9=171 (people).

Current girls: 325-171=154 (person).

1.2 3 (1-2 3) 2 kg.

2.60 (5*5*5) dm.

3.384 6 64 64 8*8 8*12 96 cm.

4.512 8*8*8 1 lap has 8*4 32 cm 256 32 8 laps.

5 240 5 24 1152 1152 * 2 3 768 kg

8.Set the water depth x m, 18 * 8 * x 720 x = 5 m (when the specific gravity of water is 1).

9.10.30*42% 15% 84kg.

11 140 (1-1 4-1 3) 336 km.

12.The number of boys transferred out is 25-16 9

Number of boys 9 5% 180

The number of male students is 180-9,171.

The number of female students is 325-171,154.

This question must be checked to determine which answer is correct (the key point is that 180 is the number of male students from last semester, and the question is about this semester).

1, 2 kg 2 3 1 2 3 2 (kg).

2. 24cm 60 liters = 60 cubic decimeters 60 5 5

3. 96 512 cubic centimeters = 8 cubic meters 8 12 96

4. 8 circles 512 cubic centimeters = 8 cubic 256 8 4 8 circles

8. Solution: Set the water depth x meters.

18×8x＝720

144x＝720

x 5 A: The water depth is 5 meters.

9. Answer: Save 10.

10. I don't think the title is clear, does 30 kg of alcohol solution contain the amount of alcohol, I won't do it! I'm sorry!

A: A and B are 336 kilometers apart.

12, 25 9 5 180 people

Boys: 180 1 5 171

Girls: 325,171,154

A: There are 171 boys and 154 girls.