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Calculators can help us with math problems,
Calculators can help us (to) do the maths problems.
A car from a to B, the first one-third of the road is ordinary road, the rest of the road is highway, only cars have been running on the ordinary highway speed of 60 km H
The speed of driving on the highway is 100 km h. The car shares 2.2 h from a to B. what is the distance between a and B?
Linear equation of one variable
Let the distance between two points AB be x kilometers
X/3÷60+2X/3÷100=2.2
X/180+X/150=2.2
11X/900=2.2
X=180
The distance between a and B is 180 kilometers
A car from a to B, the first third of the road is ordinary road, the rest of the road is expressway. It is known that the speed of the car on the ordinary road is 60km / h, the speed on the expressway is 100km / h, the car from a to B has driven a total of 2.2h, This paper puts forward a single variable linear equation to solve the "distance" or "time" of the car, and writes out the solution process?
Set the travel time of ordinary highway as X and that of expressway as y
X+Y=2.2
60X*2/3=100Y*1/3
That is, x = 2.2-y
120X=100Y
120*(2.2-Y)=100y ---- 264-120Y=100Y ---- 220Y=264
We get y = 1.2
X=1
A section of road, a car 30 minutes driving two-thirds, so how long can the car complete the journey?
30 △ 2 / 3 = 45 minutes
In a math test, the average score of the whole class is 91.2. There are 21 girls, 92 points on average, and 90.5 points on average for boys. There are () boys in this class
A. 26B. 25C. 24D. 23
(92-91.2) × 21 ^ (91.2-90.5) = 0.8 × 21 ^ 0.7 = 16.8 ^ 0.7 = 24 (people). Answer: there are 24 boys in this class
In a math test, the average score of the whole class is 91.2. There are 21 girls, 92 points on average, and 90.5 points on average for boys. There are () boys in this class
A. 26B. 25C. 24D. 23
(92-91.2) × 21 ^ (91.2-90.5) = 0.8 × 21 ^ 0.7 = 16.8 ^ 0.7 = 24 (people). Answer: there are 24 boys in this class
The average score of a five-year class in a math exam is 90, and the total score is () 68 (). How many students are there in this class?
There are 52 students in a five-year class with an average score of 90 and a total score of (4) 68 (0)
In one exam, the average score of the students in the math interest group is 70. Among them, 3 / 4 of the students pass, their average score is 80. What is the average score of the students who fail? (please give the process and explain)
This kind of problem can be solved specially
Suppose there are only four students in the exam
The average score is 70, so the part is 70 * 4 = 280
Three quarters of the students passed, with an average of 80
Then 80 * 4 * 3 / 4 = 240 points
So 280-240 = 40
It's the average of the students who failed
There are 40 students in a six-year class. In a math exam, the average score of the top 15 students is 10 points higher than that of the whole class. How many points is the average score of the rest students lower than that of the whole class?
(10 × 15) △ 40-15, = 150 △ 25, = 6 (points); a: the average score of other students is 6 points lower than that of the whole class
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