How to solve (x + 20) * 3 / 4 + x = 120)

（x+20）*3/4+x=120
0.75x+15+x=120
0.75x+x=120-15
1.75x=105
x=105/1.75
x=60

120/(x+20)+1=120/x

120 / (x + 20) + 1 = 120 / X both sides of the equation multiply x (x + 20)
120x+x(x+20)=120(x+20)
120x+x²+20x=120x+2400
x²+20x-2400=0
(x+60)(x-40)=0
X + 60 = 0 or x-40 = 0
X = - 60 or x = 40
Test: substitute x = - 60 into x (x + 20) = - 60 × (- 60 + 20) = 2400 ≠ 0
Substituting x = 40 into x (x + 20) = 40 × (40 + 20) = 2400 ≠ 0
So: x = - 60 and x = 40 are the roots of the original equation

1.05 cubic meters = how many cubic decimeters? 3 liters = () cubic decimeters = () cubic centimeters?

1.05 m3 = 1050 cubic decimeter
3L = (3) cubic decimeter = (3000) cubic centimeter

Give me some equations of grade one to solve practical problems~
Thank you ~ ~ ~ any question is OK! But... It's better to have an answer! You can be right after you finish it! Thank you ~ ~ ~ there are rewards!

1. The distance between Party A and Party B is 180km. The express train runs from Party A to Party B at the speed of 40km / h. After 30 minutes of departure, it stops for repair due to machine failure. At this time, the local train runs from Party B to Party A at the speed of 30km / h. It is known that the express train repairs for 20 minutes. How long does the local train start?
2. Two speedboats travel back and forth between a and B on both sides of the lake. If a starts from a and B at the same time and is 300 meters away from B at the first meeting, find the distance between a and B
3. From the summer camp to the school, leisure mountain and then take the level road. A student first rode a bicycle down the mountain at the speed of 12 kilometers per hour, and then took the level road at the speed of 9 kilometers per hour. It took 55 minutes to get to the school, When he came back, he passed the level road at the speed of 8 kilometers per hour, and went up the mountain at the speed of 4 kilometers per hour to return to the summer camp. It took 1 and 2 minutes of an hour. How many kilometers from the summer camp to the school?
4. Xiao Ming walked along the road, and a car came to him. He asked the driver, "is there a bicycle behind?" the driver answered, "I passed a bicycle 10 minutes ago. Xiao Ming asked," what's your speed? "Driver: 75 km / h. Xiao Ming walked on for 20 minutes and met this bicycle. Xiao Ming estimated that his walking speed was 3 km / h, What's the speed of this bike?
5. There is a distance of 450 km between AB and B. vehicles a and B start from AB and run in opposite directions. It is known that the speed of vehicle a is 120 km / h, and that of vehicle B is 80 km / h. After t hours, the distance between the two vehicles is 50 km, then t is ()
A. 2 or 2.5 B.2 or 10 c.0 or 12.5 D.2 or 12.5 D
6. A class from a to B, 20 kilometers apart, half of them take a car first, the other half walk first, they start at the same time, the first driver gets off at B on the way to walk instead, let the car immediately drive back to pick up the other half of the walkers, make them make a car to B, the result, two teams arrive at the same time, the known walking speed is 8 kilometers per hour, the car speed is 40 kilometers per hour, How many hours did it take from place a to place B?
First question:
The question is not clear, "how long does the local train leave?" then, how long does the two trains meet?
Set the starting time of local train as X
30x + 40*30/60 + 40(x-20/60) = 180
X = 52 / 21 (hours)
Second question:
The conditions are not enough. I don't know the speed of the two speedboats
If the speed is the same, the distance between a and B is 600m
If the speed is different, let a speed be x and B speed be y. The total distance is Z
Time conservation: Z / (x + y) = 300 / y, so z = 300 (x + y) / y
Third question:
Let the length of the flat road be x, and the way down the mountain (to the school is down the mountain, to the summer camp is up the mountain) be y
y/12 + x/9 = 55/60
x/8 + y/4 = 3/2
The solution is: x = 6; y = 3
Therefore: the total distance is 9 km
Fourth question:
Let the bicycle speed be X
x（10+20）/60 + 3*(10+20)/60 = 75*10/60+3*10/60
The solution is x = 23 (km / h)
Question 5:
120t + 80t + 50 = 450
Or 120t + 80t - 50 = 450
The solution is t = 2 or 2.5, so choose a
Question 6:
Suppose that the time for transporting the first batch of people is x and the time for transporting the second batch of people is y
8x + （40x-8x）*8/(40 + 8）+ 40y = 20
40x + （40x-8x）*8/(40 + 8）+ 8y = 20
The solution is x = 3 / 8; y = 3 / 8
The total time is: x + (40x-8x) / (40 + 8) + y = 1 (hour)

0. (100 zeros) 56 / 0. (99 zeros) 7 =? How to calculate the comprehensive formula~
Is equal to
=0.56/7
=0.08

If 100 zeros are removed at the same time, the formula is equal to 0.56/7 = 0.08

1 / 3 radical y + y radical 4 / Y - radical 36Y

(1/3)√y+y√(4/y)-√(36y)=(1/3)√y+2√y-6√y=(-11/3)√y

Fourth grade mathematics midterm questions

1、 Direct write the number 25 × 4 = 13 × 6 = 24 + 16 × 3 = 44 + 36 = 47 + 36 = 58-44 + 16 = 36 △ 9 = 27 △ 9 = 15 + 14-3 = 2

Simple calculation of 7 and 13 / 15 * 30

7 13 / 15 * 30
=（7+13/15)*30
=7*30+(13/15)*30
=210+26
=236

Feeling composition after success
About 400 words

In one's life, there are many things to go through. Among them, there are many failures. In the face of failure, different people will have different attitudes. When some people hear that they have failed in doing something, they will fall down and abandon themselves all day long. While others are different. In the face of failure, they will always actively look for the reasons for failure and start all over again

Sixth grade mathematics high quality class volume two test paper sixth big question four small questions

The length of a cuboid is 6 decimeters, the width is 5 decimeters, and the height is 4 decimeters. What is the volume of the largest cylinder?
It can be divided into three cases: (1) take 4 as the height of cylinder: 3.14 * 5 / 2 * 5 / 2 * 4 = 3.14 * 6.25 * 4 = 78.5
(2) Take 5 as the height of cylinder: 3.14 * 4 / 2 * 4 / 2 * 5 = 62.8
(3) Take 6 as the height of cylinder: 3.14 * 4 / 2 * 4 / 2 * 6 = 75.36
By comparison, it is found that the first case is the largest, that is, the largest cylinder is 78.5 cubic decimeters

How to solve (x + 20) * 3 / 4 + x = 120)