Some math problems, I don t know, help

Question 1: Hongguang Primary School.

There are 510 students in grades 4, 5 and 6, of which the number of students in the fourth grade is 3 4 in the fifth grade, and the ratio of the number of students in the sixth grade to the number of students in the fifth grade is 4:5How many fewer students are in 4th grade than 5th grade?

4th Grade: 5th Grade 3 4 = 3:4 = 15:20

6th Grade: 5th Grade 4:5 16:20

4th Grade: 5th Grade: 6th Grade.

50 people. There are 50 fewer students in the fourth grade than in the fifth grade.

Question 2: A project, A and B together, completed in 12 days. If A does it for 10 days and B does it for 9 days, there is still 1 5 of the whole project left unfinished. If A does it alone. How many days does it take?

It takes x days to set the armor.

9*1/12+(10-9)*1/x=1-1/51/x=1/20

x=20 The third question: The bookcase has two layers of books, the upper and lower layers, and the number of books on the upper layer is 7 8If you take 15 books from the lower layer and put them in the upper layer, then the number of books in the lower layer is 1 2 of the upper layer. How many books did the upper and lower classes have?

Set the original lower level has x copies.

7/8*x+15)*1/2=x-15

7/8x+15=2x-30

9/8*x=45

x=4040*7 8=35 copies.

A: There are 35 copies on the upper floor and 40 copies on the lower floor.

Question 1: If the fifth grade is x, then the fourth grade is three-quarters x, and the sixth grade is four-fifths x, and list the formula x + three-quarters x + four-fifths x = 510 solution x=200 three-quarters x=150 There are 150 people in the fourth grade, tell your teacher that there will not be more people in the fourth grade than in the fifth grade, because the number of people in the fourth grade is three-quarters of the fifth grade.

Let the range of f(x) at x>=0 be [m,n].

Any three numbers within the range can form a triangle.

m m n when we know m+m>n

So 2m>n>0

f(x)=1+(k-1)x/(x^2+x+1)=1+(k-1)/(x+1/x+1)

f(0)=1

x+1/x>=2

Discuss k.

The range f(x)>1 f(x)<=1+(k-1) 3 at k>1 is [1,1+(k-1) 3].

2>1+(k-1) 3>0 depends on k<4

The range of f(x)<1 f(x)>=1+(k-1) 3 at k<1 is [1+(k-1) 3,1].

2*(1+(k-1) 3)>1>0 The solution depends on k>-1 f(x)=1 when 2k=1

In summary-1 2

It is 50 decimeters long and 35 decimeters wide.

The greatest common divisor of length and width is 5 decimeters.

50*35 (5*5)=70 pieces.

Short division yields: (50,35)=5

That is to say, Xiaohuajia has two options for paving tiles: 1*1 and 5*5 From the perspective of the gaps, there are many gaps in 1*1, which saves materials, and from an economic point of view, 1*1 is more convenient and cost-saving, so I choose 1*1 square floor tiles.

A total of (50*35) (1*1) = 1750 floor tiles.

50=5*2*5

Their common factor is 5

So use 5dm bricks.

50 and 35, the greatest common divisor is 5, choose a brick with a side length of 5 decimeters. Requires 10*7=70 blocks.

The two triangles are congruent right triangles, and we align their corresponding sides to create the four convex quadrilaterals below.

Obviously, two right triangles are congruent.

To make a convex quadrilateral, you can only put equal sides together. Glued together with three equal edges, three different quadrilaterals can be obtained.

For example, the short right-angled edges are adhered to obtain a parallelogram with a long right-angled edge and an hypotenuse side of the side length.

The long right-angled edges are adhered to obtain a parallelogram with a short right-angled edge and an hypotenuse with an edge length.

The hypotenuse is adhered to obtain a long right-angled side and a short right-angled edge as a rectangle of side length.

Hello, Yao Ben.

The 2-hour journey accounts for 1 3 of the whole journey

Another 60 kilometers, accounting for 1 2 of the whole journey

So the distance between A and B: 60 (1 2-1 3) = 60 6 = 360 (km) Answer: A and B are 360 km apart.

60/(1/2-1/4)=240

A and B are 240 kilometers apart.

The ratio of the distance traveled in 2 hours to the whole journey is 1:3, and the distance traveled per hour is 1 6 of the whole journey. Another 60 kilometers is half of the whole journey, then 60 kilometers can be traveled in 1 hour, and the whole journey takes 6 hours, so the whole journey is 360 kilometers.

Have you learned equations? Make an equation.

If the two-hour journey is x, the whole journey is 3x; The equations can be listed as follows according to the title:

2*(x+60)=3x;

then it can be solved, x=120;

3x=360；

So the distance between A and B is 360 kilometers...

Hours = (2) hours (9) minutes.

1.Rewrite (95678000) to "10,000" as the number is 10,000, and omit the mantissa after "100 million".

2.The 5-meter-long steel bar was sawn into small sections of the same length as each section, sawed 6 times in total, and each section accounted for the total length of (1) (7) and each section was (5 7) meters long.

3.In the brine with 30% salt, add 6 grams of salt and 14 grams of water, and the salt content percentage of the salt water is (30%)

4. A project, team B alone to do it takes 8 days to complete, team A alone to do 10 days, now the two teams do it together, how many days after there is still this project? (4 days later there was still 1 10 left in this project, 9 40 per day).

a 5 b (a and b are not equal to 0), then a and b (a:b=5:1) proportional relationship.

8 and the ratio of all its divisors is (8) 4 ) 2 ) 1).

In brine containing salt 3, the ratio of salt to water is 3 97.

Hour 9 minutes.

100 million, 100 million. 5 7 meters.

5.Working together for 4 days, there are still 4 9 left to complete.

8.That's right.