When a car drives from city a to city B, the ratio of the distance traveled to the distance not traveled is 1:3. If it travels another 130 kilometers, the ratio of the distance traveled to the distance not traveled is 5:2. A, how many kilometers are there between the two cities?

When a car drives from city a to city B, the ratio of the distance traveled to the distance not traveled is 1:3. If it travels another 130 kilometers, the ratio of the distance traveled to the distance not traveled is 5:2. A, how many kilometers are there between the two cities?

1 / (1 + 3) = 1 / 4 of the total
What has been done now accounts for 5 / (5 + 2) = 5 / 7 of the total length
So the distance of AB is 130 / (5 / 7-1 / 4) = 280

There are 185 red, white and black beads of the same size. They are arranged in the order of 5 red, 4 white and 3 black. How many black beads are there? What color is the 69th bead?

According to the meaning of the title, every 5 + 4 + 3 = 12 beads is a cycle; (1) 185 ^ (5 + 4 + 3), = 185 ^ (12), = 15 5, there are 15 cycles, the remaining 5 beads are red, the remaining black beads are: 15 × 3 = 45; a: there are 45 black beads. (2) 69 △ 5 + 4 + 3, = 69 △ 12, = 5 There are 5 cycles in it, the remaining 9 beads are 5 red and 4 white, the remaining 69th is white. A; the 69th is white. So the answer is: 45, white

Application of area
A cuboid glass fish tank without cover, 6 decimeters long, 3 decimeters wide and 4 decimeters deep
(1) How many square decimeters of glass do you need to make this fish tank?
(2) How much water is there in the fish tank (the thickness of the glass is not considered in the calculation)?
2. The original water volume of a reservoir is certain, the river water is put into the reservoir evenly every day, 5 pumps can be drained for 20 days in a row, and 6 pumps can be drained for 15 days in a row. If it is required to be drained for 2 days, how many pumps are needed?
3. Two cars run from two places 689.5km apart at the same time. Car a runs 52km per hour, while car B runs 45km per hour. After 2 hours, car B breaks down and repairs for 3 hours before moving on?

1. The first question is actually to calculate the surface area, but it should be noted that the fish tank has no cover, s = 2x (6x4 + 3x4) + 6x3 = 90 square decimeters. The second question is to calculate the volume, but at this time the bottom area is the same as the fish tank, and the water depth is v = 6x3x1.5 = 27 cubic decimeters