Speed = distance/time, 240/ 1.2 = 200 km.
The remaining distance is 400 kilometers, and the sum of AB car speeds is 200 kilometers, and 400/200 = 2 hours.
(Question 2): Whole journey =(80×3-50)×2=380 km.
Vehicle speed b = (380-80 * 3-7) ÷ 3 =133/3 km/h.
(3) Question 1. Vehicle speed a: 60 * 4/3 = 80 km/h.
2。 (80+60)*4=560 km
(Question 4), suppose the speed of the express train is X and the speed of the local train is Y.
X +Y=960/6
10X=960
Solve x with 96 and y with 64.
(Question 5), the speed ratio of passenger and freight vehicles is 3 to 2. Let the common ratio be k.
Bus speed =3k
Truck speed =2k
3k+2k=720/3.6
5k=200
k=40
Bus speed = 3k = 3 * 40 =120m/h.
Truck speed = 2k = 2 * 40 = 80m/h.
(6 questions),
First of all, because the score difference of each game is no more than 4 points, but the total score of China team is 9 points more than that of Korean team, so if the score difference of the first game is not 4 points, it is 3 points, 2 points, 1 point. This will definitely not reach the gap of 9 points. So the first game must be four points short. This is calculated in reverse. It is not difficult to calculate that the scores of the three sets are 4 points, 3 points and 2 points respectively.
In volleyball match, if the score is 2 points ahead, win first if it reaches 25 points.
Played three times.
The first game is four points short, and the condition of leading by two points must be met. So China scored 25 points. South Korea's score of 25-4 is 2 1.
The second game was 3 points short, which also met the requirements, so China scored 25 points. South Korea scored 25-3 or 22 points.
The third inning is two points short, so there are two possibilities. The first one is China 25, Korea 23. But in this case, South Korea's total score is less than 69. That is to say, South Korea's score should be 69-22-2 1, which is 26 points. In this case, the 26+2 China team will get 28 points.
(Question 7), two adjacent prime numbers are (2) and (3), and two adjacent composite numbers are (8) and (9).
(8 questions),1/(1/2+1/3+1/6) =1(hours)