Troubleshooting math problem 1, math problem troubleshooting

c.Monitor the temperature. There is no point in monitoring the temperature, because room temperature can never ignite gas.

3rd grade. The total number of students in classes 2 and 3:

50-45=105 (person).

The number of students in the third class is the same as that in the second class.

105 divided by 2 = person).

Let ab=ac=a, bc=b, get.

a+a/2=12,b+a/2=15；

or a+a 2=15, b+a 2=12;

The solution is a=8, b=11, i.e., ab=ac=8, bc=11 or a=10, b=7, i.e., ab=ac=10, bc=7

From the question, it is known that the total value of the perimeter is 3 different from BC, and there are two cases, one AB is long and BC is short;2. Ab short BC long back to calculate yourself.

60°。。The main thing used in this problem is the theorem: the hypotenuse of a right triangle is equal to half of the hypotenuse.

Because: isosceles trapezoidal.

So: ad=bc

Because: dc ab ad ec

So ad=ec=bc dc=ae

Because e is the midpoint.

So: ae=be

So: ae=be=dc

Because abc is a right triangle ae=be

So ec=be

So ec=bc=be

The equilateral triangle is 60°

Because AB is parallel to CD and EC is parallel to AD

So AECD is a parallelogram.

So ad=ec

And because of the isosceles trapezoidal ABCD

So ad=bc=ec

Because abc is a right triangle and e is the midpoint of ab, it can be seen that the middle line on the hypotenuse of a right triangle is half of the hypotenuse: ec=be

So bc=ec=be

Therefore, BEC is an equilateral triangle.

Angle abc = 60 degrees.

60 degrees. Because the triangle ABC is a right-angled triangle and CE is the midline, in a right-angled triangle, the midline on the hypotenuse is equal to half of the hypotenuse, so CE=AE=BE, so the triangle CEB is an isosceles triangle, so CE=BE, because AB is parallel to CD and EC is parallel to AD, so the quadrilateral AECD is a parallelogram, so 6 angles B is equal to 360 degrees, so angle B is equal to 60 degrees.

Note that the middle line of a right triangle is equal to half of the hypotenuse, and abc= ceb, so bce is an equilateral triangle.

Hello! One: "Question: Peach three plum four olive seven.

Contents: A peach is 3 points, a plum is 4 points, olives are seven 1 point, buy a total of 100 peaches and plums with 1 yuan, ask how many peaches and plums and olives to buy? Answer: Let's buy x peaches, y pears, and z olives.

x+y+z=100 (1)

From the title: 3x+4y+1 7*z=100 (2)(1), x+y=100-z (3)(1)*7-(2), 20x+27y=600 (4) because z is a multiple of 7.

So z = 7, 14, 21 ......98

This equation is experimented with known conditions.

The results of the experiment yield x=3

y=20z=77

A: Buy 3 peaches, 20 pears, and 77 olives. 》。

2: "Question: Spiders have 8 legs, dragonflies have 6 legs.

Existing spiders. Several dragonflies. They have a total of 180 legs, and the ratio of dragonflies to spiders is 2; 3

How many are there? Answer: Suppose there are 2x dragonflies, then the spider is 3x, 2x*8+3x*6=180 gives x=5, then there are 10 dragonflies and 15 spiders. 》。

Hello, what are you talking about?

yes, wordless questions are so difficult.

My God, this topic is really difficult!! It's too hard.

One outer angle of the triangle is equal to the sum of the two inner angles that are not adjacent to him, so the angle adc = the angle bad + the angle abc

Angular adc=a angular bad=b

Then a=b+angular abc

Angle abc = a-b

Since this triangle is an isosceles triangle, then the angle acb = angle abc = a-b if cd = ab then cd = ca then the angle cad = angle adc = a then the angle acd = 180° - angle cad - angle adc = 180 ° - 2a so a-b = 180 ° - 2a

3a-b=180°

acb=180°-2a

and acb= abc (isosceles), abc+b=a (the outer angle is equal to the sum of two inner angles not adjacent to it).

180°-2a=a-b

3a=180°+b

cd=ab=ac

The triangular CDA is an isosceles triangle with an angle of 180°-2A in the triangular CDA

A straight-edged triangle with an edge longer than 1 and an area of 10 can only have a right-angled side of centimeters. It becomes a square with a side length of 29 kai, with an area of 29, and a square with a side length of 3 and an area of wax branch 9

Supplementary question: It's very simple, I don't know if I'm talking about Wheel Yumin, because ** is not easy to pass, that is, start cutting on the two long sides of the left and right sides 1 meter out, cut to 2 meters respectively, and then directly connect the two points to cut, and then rotate one of the pieces 90 degrees.

According to the title, a right triangle larger than 1 with an area of 10 can only be a right angled with centimeters. It becomes a square with a side length of 29 kai.

The area is 29, and the middle circumference is changed to a square with a side length of 3, and the area is 9

Supplementary question: It's very simple I don't know if what I'm saying is clear Because ** is not easy to pass, it is to start cutting on the two long sides of the left and right sides 1 meter out, cut to 2 meters respectively, and then directly connect the two points to cut it, and then rotate a piece of it 90 degrees.

From the question, it can be seen that the side length of a right-angled triangle can be 2,10 or 4,5, and the corresponding products of the four square surfaces are respectively dismantled

The front brigade is formed by making the beveled side as a large square side.

Inspired by Weixing 2010, it can also be enclosed into two right-angled edges added together to make a large square edge, and the hypotenuse side is a small square edge, at this time, the corresponding square area is

Thank you, Weixing 2010

1+2+……n=n(n+1)/2

>1/(1+2+……n)=2/n(n+1)=2[1/n - 1/(n+1)]

> Original = 2*[1-1 2 + 1 2-1 3 +....1/99-1/100 + 1/100-1/101]

Split term method, very common.

Answer: Let's assume that Uncle Li's actual salary income for this month is x yuan.

Suppose Uncle Li's tax range is $500; Then, the equation is: (x-2000)*5%=190 x=5800 yuan, and then x=5800 yuan into the original formula, the tax payment equation is: (5800-2000)*15%=570 yuan, therefore, this scheme is not valid.

Suppose Uncle Lee's tax range is $500, $2000;The equation is: (x-2000)*10%=190 x=3900, and then x=3900 yuan is brought into the original formula, and the tax payment equation is: (3900-2000)*10%=190 yuan, therefore, this scheme is valid.

Suppose Uncle Li's tax range is 2000 yuan, 5000;The equation is: (x-2000)*15%=190 x yuan of the solution, and then bring x=yuan into the original formula, and the tax payment equation is: (yuan, therefore, this scheme is not valid.

Therefore, Uncle Li's actual salary income this month is 3,900 yuan.

This question has been completed, my ability is limited, if there is anything wrong, please correct, thank you!

First of all, he must be more than 2000 yuan, but between 500-2000 yuan.

Suppose his actual salary income for this month is x yuan.

500×5%+（x-500)×10%=190x=2150