A car drives from a to B at an average speed of 20 kilometers per hour. After arriving at B, it returns to a at a speed of 30 kilometers per hour A car drives from a to B at an average speed of 20 kilometers per hour. After arriving at B, it returns to a at a speed of 30 kilometers per hour. It takes 7.5 hours to get the distance between a and B. [the answer is 90 kilometers] [the process] [the equation of one yuan once] [thank you!]

Let the distance be X
Then the total time is x / 20 + X / 30 = 7.5
(1/12)x=7.5
x=7.5÷1/12=90
So the distance is 90 kilometers

RELATED INFORMATIONS

1. The diameter of a car's outer tire is 5 decimeters, and the wheels roll 400 cycles per minute. How many kilometers does the car advance per hour Pay attention to unit conversion
2. AB and B leave each other at the speed of 75 km / h and 60 km / h respectively. When they meet, they travel 60 km more than B. what is the distance between the two places -- help me. 50 more if you can
3. The two trains run from a and B at the same time. They meet in 5 hours. After 7 hours, the distance between the two trains is 280km. What is the distance between a and B? A better way
4. There are 40 baskets of apples and pears in the fruit supermarket. Each basket of apples is 20 kg, and each basket of pears is 25 kg. The number of kilograms of apples is 80 kg more than that of pears. How many baskets of apples and pears are there?
5. In the triangle ABC, ab = AC, the perpendicular of AB intersects at point E, ab = 6cm, and the circumference of the triangle EBC is 10cm. Find the length of BC
6. In Δ ABC, e is a point on the bisector of ∠ ACB, ∠ CAE = ∠ CBE, the extension of CE intersects AB at D, and CD ⊥ AB is obtained
7. E is a point in triangle ABC. Try to prove that angle CAE + angle CBE + angle c = angle ABC E is a point in triangle ABC. Try to prove that angle CAE + angle CBE + angle c = angle ABC
8. ① Let the three sides of △ ABC be a, B and C respectively, and try to prove that: a < 12 (a + B + C). ② let the four sides of a quadrilateral be a, B, C and D in turn, and the two diagonals be e and f respectively, and prove that: e + F > 12 (a + B + C + D)
9. As shown in the figure, a, P, B and C are four points on the circle O, angle APC = angle CPB = 60 degrees. Judge the shape of triangle ABC and prove it
10. As shown in the figure, in △ ABC, AE is the angular bisector, and ∠ B = 52 °, C = 78 ° to find the degree of ∠ AEB
11. A freight car and a passenger car leave from two places at the same time. After 4 hours' meeting, it takes 12 hours for the freight car to complete the whole journey, and how many hours for the passenger car to complete the whole journey? You can't just have the answer
12. 1. There are four story books and three science and technology books in the bookcase. We should ensure that we can take out two story books at a time, and at least how many books at a time? 2. There are 45 students in the class. How many exercise books can the teacher give to everyone at least to ensure that at least one person can get two or more? 3. There are three different natural numbers, and at least two numbers can be found to make their difference even. Why? 4. There are 20 children in the kindergarten, and now there are 64 pieces of chocolate candy, Does anyone get four or more balls? 5. Ten balls of three colors are packed together to ensure that they can get two balls of the same color at a time. At least how many balls should be taken at a time? 6. There are enough balls of four colors in the bag to ensure that six beads of the same color can be found. At least how many beads can be found? I have urgent need
13. Using 3,4, - 6, - 10, write three different formulas through mixed operation, so that the result is equal to 24
14. 11,12,13,16,17,20,25,24, () fill in a number in brackets to make it conform to the arrangement rule of the original sequence
15. What are the missing numbers in the brackets of series 0, 5, 8, 17, (), 37?
16. The nine numbers 1, 2, 3, 4, 5, 6, 8, 12 and 24 are respectively filled in the small circle of the graph, so that the product of the multiplication of the three numbers of each line is equal 0-0-0 0-0-0 0-0-0 Nine circles up and down, left and right, cross, multiply three numbers, the product is all equal
17. Three. But please do it as soon as possible 1. The arc length of a sector is 4 π. Use it to make a side of a cone. Find the bottom radius of the side 2. In a circle O with a radius of 25 cm, the lengths of two parallel strings are 40 cm and 14 cm respectively. What is the distance between the two parallel strings? 3. A circle with a diameter of 24 cm. The maximum side length of an equilateral triangle that can be completely covered shall not exceed cm
18. The experimental primary school held a group performance on campus. The ratio of the number of participants in grade 3, 4 and 5 was 2:5:3. It is known that the number of participants in grade 3 was 46. How many participants in grade 4 and 5? Although there is no point! But I hope you can have a warm heart! Please list the formula
19. The quality of grain stored in warehouse A and warehouse B is equal. After 8 tons of grain is taken from warehouse A and put into warehouse B, the quality ratio of grain stored in warehouse A and warehouse B is 4:5? (please use proportion solution)
20. A, B and C make a total of 940 parts at the same time. It takes 5 minutes for a to make one, 25% more than that for B, and 2 / 5 less than that for a, respectively I can answer this question, but I don't understand why B takes 5 / (1 + 25%) = 4 minutes more than 25% is not B, not 5-5x25%