"Teacher Tao, I lost my admission ticket at home, what should I do now?"

Ren Changjiang on the other end of the phone looked very anxious, and his voice sounded crying. When he left in the morning, he obviously remembered to bring everything with him, but he felt uneasy halfway through, and when he flipped through his schoolbag, he found that the admission ticket was not in it, and he rummaged through the entire schoolbag, Ren Changjiang still didn't want to find it, and after thinking about it carefully, he remembered that it should be when he had breakfast, and when Ren Yan and Hu Fei helped him check things, he took it out and forgot to put it back.

In a hurry, Ren Changjiang's first thought was to call Tao Li for help. Fortunately, he listened to his father Ren Yan's words this morning and brought his mobile phone with him, otherwise he would have to be in a hurry now.

"How did you get here, what about your father, is he on the side?" Tao Li didn't expect that Ren Changjiang would really forget what he had told him thousands of times. I used to have the things that appeared in the newspaper every year in the college entrance examination, but I actually experienced it myself!

"I'm here on my own, Mr. Tao. What should I do now!" Ren Changjiang said as he stood on the side of the road, crying.

Originally, Ren Yan and Hu Fei were going to send Ren Changjiang to school for the exam, but Ren Changjiang did not agree, for this exam, Ren Yan's family specially bought a house not far from Jinling Middle School a month ago, which is convenient for Ren Changjiang to go to and from school, and it takes about fifteen minutes one way to drive.

But who knew that such a thing could happen!

"Don't cry yet, you're coming alone...... By the way, do you have any money with you?" Tao Li forced himself to calm down, if he panicked at this time, then this matter would really be difficult to solve.

"I brought it. Ren Changjiang nodded desperately and said, but the tears couldn't stop flowing down.

"Where are you now?" asked Tao Li quickly.

"Renmin Middle Road, near Suning Square. Ren Changjiang looked around and replied.

"Your parents are in that house on Jiefang Avenue now, right?" Tao Li knew about the family's newly bought house. He now needs as much information as possible to help him make a decision.

"Yes, my mom is at home, and my dad is going to a meeting. Ren Changjiang replied.

"People's Middle Road...... Liberation Street. ”

Tao Li closed his eyes and began to try his best to recall all the road conditions along the way. As a native of Jinling, Tao Li is very familiar with most of the road conditions in the city, and there is still half an hour before the start of the exam, but if he is more than fifteen minutes late, he will not be able to enter the examination room, so he has to find the fastest way to let Ren Changjiang arrive at the school safely after getting the admission ticket within forty-five minutes.

"From Renmin Middle Road to Jiefang Avenue, if you take a taxi, the nearest road is to turn right directly from Nanhu Avenue into Jiefang Avenue, but there are a total of five traffic lights on this road, and the time to skim the yellow light is not counted, each traffic light, the time of the green light is about 40 seconds, and the time of the red light is 20 seconds, so that in each independent traffic light, the probability of encountering a red light is one-third, and the probability of encountering a green light is two-thirds. ”

Tao Li's brain is running wildly, generally speaking, the green light time of motor vehicles is much longer than the green light time of pedestrians, the specific time Tao Li is not clear, but reasonable assumptions are also valid.

"Take the road of Nanhu Avenue, there is a total of about 10 kilometers of distance, that is to say, there will be a traffic light every 2 kilometers on average, the car is walking on the city road, and there are no speed limit signs but there are marked roads, according to the requirements of the regulations, there is no road center line of the road, the speed limit of urban roads is 30 kilometers per hour, there is only one motor lane in the same direction, the speed limit of urban roads is 50 kilometers per hour, both roads are available on this round of roads, and the average speed is 10 kilometers per hour. ”

"Even if there is no traffic jam, the green light along the way, it takes half an hour to go back and forth, and the probability of a green light is only 32/243, assuming that the taxi will stop when it encounters a red light or arrives at the destination, then for the number of times the car stops, then the distribution column of the number of stops is a discrete independent probability problem, so that the expected value of the number of stops is ...... 355/243, the maximum time for each stop is 20 seconds, so it will take about a minute to wait for the red light back and forth, plus it is the morning rush hour, there will be a traffic jam, and it is difficult to rush back to school within 45 minutes!"

Tao Li quickly overturned the method of taking a taxi home in a dozen seconds, so that he could only ride a bicycle!

"From Renmin Middle Road to Jiefang Avenue, there is a small road, there is no traffic light on the road, only 8 kilometers each way, if this time let parents take the admission ticket, while riding, two people in the opposite direction, so that everyone only needs to ride 4 kilometers, normal people ride a bicycle at a speed of about 15 to 20 kilometers per hour, even if it is the slowest 15 kilometers per hour, it only takes 32 minutes to go back and forth, if it is a little faster, it does not even take half an hour, at the same time I am now riding an electric car from the school, it only takes less than five minutes to the People's Middle Road, continue to ride, so that he gets the admission ticketI'll be able to pick him up on his way back, and I'll be able to get to school by nine o'clock by electric car!"

That's right, it's a bike walk!

In this lightning and flint one minute, Tao Li used the mathematical knowledge he learned to perfectly find a way to solve the current problem!

"Xiao Jiang, remember the path I took you home last time! Ride a bicycle on that path, I will let your parents take the admission ticket and ride on that road, the teacher has calculated, the time is definitely enough, you don't panic, you don't need to ride in a hurry, just be a little faster than when you usually go to school, be careful on the road." Tao Li quickly said to Ren Changjiang, Tao Li took him through that road several times.

"Got it, Mr. Tao. After Ren Changjiang hung up the phone, he immediately rode his bicycle towards the trail.

Tao Li dialed Ren Yan's phone as soon as possible, and after a few beeps on the phone, it was finally connected, "Brother, Xiao Jiang's admission ticket was forgotten at home, can you find out if it is around you?"

"What! I didn't bring the admission ticket? Xiaofei, let's take a look where Xiao Jiang's admission ticket is?" Ren Yan, who was just about to sleep for a while, was suddenly woken up, and hurriedly shouted to Hu Fei in the living room outside the house.

"I'll look for the admission ticket!" Hu Fei was obviously frightened, and hurriedly looked for it in the living room.

"Found it, under the coffee table in the living room!" Hu Fei hurriedly shouted.

"Brother, I found the admission ticket, do you want me to drive it over now?" Ren Yan hurriedly asked.

"It's too late to drive, it's the morning rush hour, and the road from your home to school is already the most congested, let alone the traffic restriction today!" Tao Li shook his head and said.

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