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The distance between station a and station B is 1280 meters. After adopting the "harmony" EMU to increase the speed, the running speed of the train is 3.2 times of the original speed Continued: the time is shortened by 11 hours. How to calculate the speed of the train after speed increase? (equation)
Let's set the speed before the acceleration as X and the current speed as 3.2X
1280/x-11=1280/3.2x
The solution is x = 80, so 3.2X = 256
I'm also working on it, by the way
A. B is 630km away from the two places. A and B trains run from the two places at the same time and meet each other in three hours. It is known that the speed ratio of a and B trains is 4:3, so we can find B train
1 hour, 630 △ 3 = 210 km
So B has no chance. It's 210 × 3 ^ (3 + 4) = 90 km
x+y=630/3
3x=4y
x=120
Vehicle B speed y = 90
A case of pure milk of "terensu" costs 65 yuan, which is 3 times less than a case of mineral water. How much is a case of mineral water?
Suppose a box of mineral water X Yuan, & nbsp; 3x-1 = 65, 3x-1 + 1 = 65 + 1, & nbsp; 3x ／ 3 = 66 ／ 3, & nbsp; & nbsp; & nbsp; & nbsp; X = 22, answer: a box of mineral water 22 yuan
The distance between the two cities is 240 km. The two vehicles run from the two cities for 2.4 hours and meet each other. It is known that the speed of vehicle a is 20 km less than that of vehicle B
What's the speed of car a and car B?
The sum of the speeds of a and B vehicles is 240 △ 2.4 = 100 km / h,
Then the speed of car B is (100 + 20) △ 3 = 40 km / h,
The speed of car a is 40x2-20 = 60km / h
A mixed algorithm of rational numbers
In words
(1) The addition rule of rational numbers: 1. Add two numbers with the same sign, and take the same sign, and add the absolute value; 2. Add two numbers with different signs, and take the sign of the adder with larger absolute value, and subtract the smaller absolute value from the larger absolute value; 3. Add a number and zero to get the number; 4. Two numbers are opposite to each other
The construction site needs to use 500m cubic meters of sand and stone, the density of sand and stone is 1.4 × 10 cubic kg / m3, transported by 5T truck
How many cars do you need to transport?
Total weight of sand and stone: 500x1.4 = 700T,
Number of vehicles: 700 / 5 = 140
It's not cost-effective to use 5 tons of cars in such a large quantity
Knowing the volume and density, the mass is 500 / 14 = 700T, 700 / 5 = 140 trucks
Xiaoming took 15 yuan to buy 4 bottles of fruit milk, 1.5 yuan per bottle, and the remaining money to buy mineral water, 2.5 yuan per bottle. How many bottles can you buy? What strategies do you find?
3 bottles, 15 yuan --- 4 bottles, X1.5 yuan / bottle = 9 yuan, 9 divided by 2.5, the maximum is 3, there is 1.5 yuan, you can buy a bottle of fruit milk
A and B start at the same time from AB and run in opposite directions. They meet three hours later. When they meet, B runs 240 kilometers. The speed ratio of a and B is 3:4, and ab is 3:4
How many kilometers are there from each other?
v2=240/3=80
v1:v2=3;4 v1=60
s=3x(60+80)=420
What is the operation order of rational numbers? Please answer as soon as possible, urgent!
The order of mixed operations of rational numbers is
First calculate the power, then multiply and divide, and finally add and subtract
The same level operation is carried out from left to right
If you have parentheses, you need to count them first
A vehicle with a load of 2.5 times the fourth power Newton (n) of 10 has to transport a volume of 60 cubic meters and a density of 2.5 times the third power kg / cubic meter of 10
How many times will it take to transport the stones? (g = 10N / kg)
The weight of stone is: g = mg = PGV = 2.5 * 10 ^ 3 * 10 * 60 = 1.5 * 10 ^ 6 n
1.5 * 10 ^ 6 / 2.5 * 10 ^ 4 = 60 times
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