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The speed ratio of the two vehicles is 7:11. After the first meeting, the two vehicles continue to move in the same direction and reach the destination respectively Return immediately after the end. When the second meeting, car a is 80 kilometers away from B. how many kilometers are there between a and B?
The distance between a and B is x km
At the second meeting, car a was 80km away from ground B, which means that car a was traveling x + 80km, and car B was traveling x + (x-80) = 2x-80km
（X+80）：（2X-80）=7：11
7（2X-80）=11（X+80）
14X-560=11X+880
3X=1440
X=480
Four hundred and eighty
The speed ratio of a and B is 7:11. After the first meeting, the two vehicles continue to move forward and return to the destination immediately. After the second meeting, the distance between a and B is 80 dry meters?
Let the total length be 7 + 11 = 18
A total of 7 * 3 = 21
therefore
Total length = 80 divided by (21-18) * 18
=480km
Party A and Party B set out from ab at the same time. They met each other head-on for the first time at a distance of 100 meters from B. after meeting, a's speed increased to 2 times of the original. After a got to B, he immediately turned around and caught up with B. when B got to a, B still had 50 meters to go. So how long is the distance between a and B?
Two hundred and fifty
A batch of goods and materials can be transported by trucks and trucks at the same time, which can be completed in 6 times. If only large trucks are used, it can be completed in 10 times. If only small trucks are used, it will take more time
How many times does it take to complete the shipment if it is transported by small truck?
1/6-1/10=1/15
1/(1/15)=15
Answer 15
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Series puzzle!
1. Let {an} satisfy: a1 + A2 / 2 + A3 / 3 + A4 / 4 +Aan / N = n ^ 2-2n-2 general term formula for sequence {an}
2. It is known that the first three terms of arithmetic sequence are 2, 4 and 6, and the sum of the first n terms is Sn, S50 = 2550
Find 1 / S1 + 1 / S2 + 1 / S4 1/sn=?
If n is greater than 1, a1 + A2 / 2 + A3 / 3 + A4 / 4 +an/n-a1+a2/2+a3/3+a4/4…… +This is the case of an = 2n ^ 2-3n-2-3n, when n = 1, A1 = 1 ^ 2-2-2 * 1-2 * 1-2-2-2-2-2-2 = -3 is not equal to 2 * 1 ^ 2-2-3-3-1 = -1, so 1 an = 2n ^ 2-3n, n is greater than 1; 2 an = 2n ^ 2-3n, when n = 1, when n = 1, when n = 1, this is the case where n = 1 is the case of n = 1.2.2 by using the known conditions, we obtain an = 2n = 2n, and Sn = Na1 + n (n (n-1) (n-1) K / N (n (n (n-1) (n-1) (n (n-1) (n-1) K / N (n (n (n-1) K / N (n (n-1) K / 1) K / N (n (n (n (n-1) K / N,
1/s1+1/s2+1/s4…… 1/sn=（1-1/2+1/2-1/3+1/3…… +1/n-1/n+1）=n/n+1
1.an＝2n^2-3n
2.1-（n/n+1）
Nah.....
A. Two cars B travel in the same direction from a and B, 40 kilometers apart. Car a is behind car B, and car a starts one hour after car B. as a result, it takes car a three hours to reach the destination at the same time as car B. It is known that the speed of car a is 2 / 3 times that of car B
If the speed of car B is V, then the speed of car a is 1.5V; if the distance between car B and destination is x, then the distance between car a and destination is 40 + X; if 1.5V * 3 = 40 + X, 4 * V = X
V = 40, so the speed of car a is 120 and that of car B is 80
Speed of car B: 40 / (1 + 3) = 10km / h
Speed of car a: 3 / 2 × 10 = 15km / h
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Speed of car B: 40 / (1 + 3) = 10km / h
Speed of car a: 3 / 2 × 10 = 15km / h
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One large truck and two small trucks can transport 3 / 10 of a batch of goods at a time. For example, four large trucks and five small trucks can transport this batch of goods at a time
(Continued) Q: only one truck is used to transport this batch of goods. How many more small trucks than large trucks?
If the one-time traffic volume of large truck is a, and that of small truck is B, and the total cargo volume is 10, then the following relationship exists: a + 2B = 34a + 5B = 10: a = 5 / 3, B = 2 / 3, using the total cargo volume of 10, we can get: all trucks (a) are: 10 △ 5 / 3 = 6, all cars (b) are: 10 △ 2 / 3 = 15-6 = 9
How to compile equidistant and unequal sequence
The number of workers in the enterprises of an industrial bureau is as follows: 5555062207338420336941654842254767288447484417731483556034331262379861621590298490450
A. The distance between B and a is 1890 km. The trains a and B start from a and B at the same time and run in opposite directions. A runs 120 km per hour and B 150 km per hour. After how long, the distance between the two workshops is 135 km?
In the problem of travel, distance = speed × time. Suppose that after X hours, the distance between the two vehicles is 135 km, then a has driven 120x km and B has driven 150x km. When the distance between the two vehicles is 135 km before meeting, the equation is: 120x + 135 + 150x = 1890. When the distance between the two vehicles is 135 km after meeting, the equation is: 120x + 150x = 1890 + 135 Or 7.5 hours, the two trains are 135 kilometers apart
Two large trucks and five small trucks are used to transport 42.5 tons of goods. A large truck is 1 ton more than twice the carrying capacity of a small truck. What is the carrying capacity of a small truck?
Make the weight of large vehicle X and that of small vehicle y
2X+5Y=42.5
X=2Y+1
Y=4.5
If the weight of a small truck is x, then the weight of a large truck is 2x + 1
There is equation 2 (2x + 1) + 5x = 42.5, and the solution is x = 4.5
So the truck weight is 4.5 tons
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