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Both Party A and Party B start from place a at the same time and follow the same route to place B. If Party A walks at the speed of a km / h for half of the time and B km / h for the other half of the time; Half of the distance of B travels at the speed of a km / h, and the other half travels at the speed of B km / h (a, B are greater than 0 and a ≠ b), then () A. A arrives at B first B. B arrives at B first C. Party A and Party B arrive at place B at the same time D. Uncertain
Let the distance from place a to place B be s, the time taken for Party A to complete the whole process is t, and the time taken for Party B to complete the whole process is t,
From the meaning of the question, a × one
2T a + B × one
2T a = s, the solution is: t a = 2S
a+b；
And t b = 1
2S
a+1
2S
b=S(a+b)
2ab；
T a
Tbe = 4AB
(a+b)2，
Because when a ≠ B, (a + b) 2 > 4AB,
So t a
T b < 1, so t a < T B. so a reaches ground B first
So choose a
Math problem. A highway is 360m long A road is 360m long. Two pairs of Party A and Party B pave the road from both ends at the same time. The speed of team a is 1.25 times that of team B. after four days, all the roads are paved. How many meters are paved by Party A and Party B each day Find all the solutions
360 ÷ 4 = 90m. 90 ÷ (1 + 1.25) = 40m repaired by the two teams in one day. 90-40 = 50m repaired by team B every day. 90-40 = 50m repaired by team a every day
The tunnel entrance on an expressway in a city is in a plane rectangular coordinate system, The tunnel entrance of an expressway in a city is in the plane rectangular coordinate system. The section of the tunnel is composed of parabola and rectangle. The length of the rectangle is 16m and the width is 6m. The parabola can be expressed by y = - 1 / 32X2 + 8 (1) There is a large cargo truck. After loading a large equipment, its width is 4m, and the distance between the top of the on-board large equipment and the road surface is 7m. Can it pass through the tunnel safely? Give reasons (2) If there are two lanes in the tunnel, can the truck pass safely? (3) For the sake of safety, how much do you think it is more appropriate to limit the height of the tunnel? Why?
(1) Substitute x = 7 into the function,
Y = 207 / 32 > 4
So you can pass safely
(2) Two way channels divide y by 2,
Y / 2 = 207 / 64
A mathematical problem Two vehicles a and B start from a and B at the same time and travel opposite each other. When vehicle a takes half of the whole journey, one vehicle is 24km away from station a; When car B goes half the way, car a is 15km away from station B. find the distance between station AB and station B
Suppose: the distance between AB and the two stations is x km
1/2x:(x-24)=(x-15):1/2x
x ²- 52x+480=0
(x-40)(x-12)=0
X = 40 x = 12 (contradictory to the meaning of the topic, omitted)
Therefore, the distance between the two stations AB is 40 kilometers
I wonder if you are a junior high school student or a primary school student. This is the problem-solving method in junior high school. I haven't come up with it in primary school
The length of a highway is 60km, and the length of repaired and unmodified highway is in proportion ()
Inversely proportional
Two engineering teams build a section of highway together (math problem) The two engineering teams repair a section of highway together. Team a repairs 168 meters from east to west every day and team B repairs from west to East. After five days, the two teams meet. It is known that team a repairs alone for 15 days. How many meters does team B repair every day? (it's better to explain the understanding of each step and teach me how to solve similar engineering problems in the future? If you list equations, don't write x =? In one step. Solve it immediately!)
168 * 15 = 2520m (calculate the total distance by using the total amount of work = work efficiency * work time)
168 * 5 = 840m (calculate the distance of class a repair in 5 days)
2520-840 = 1680m (calculate the distance repaired by Party B in 5 days)
1680 / 5 = 336m / day (total divided by speed = time)
In case of engineering problems, we should first review the problems and understand them. At the same time, we should also pay attention to the details, such as whether the units are unified. We can learn it well by grasping the formula - work efficiency * work time = total work volume. Of course, we can draw line segment diagram appropriately, which will be more convenient to solve
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