26. June 2017

Task of the Week: Red or Green?

The present Task of the Week leads to Münster and contains a question from the probability calculation.


Task: Red or Green? (Task number: 428)

The city of Münster is trying everything to make road traffic as smooth as possible. There is even a traffic light hotline, where you can make suggestions for improvement. Despite all the good planning, walkers often come to red traffic lights. Often, the red traffic lights are noticed more often than the green traffic lights. Estimate how often a traffic light shows “green” if one passes the traffic light 100 times.


In order to solve the problem, students should first measure the duration of a green phase, as well as the duration of a red phase. The duration of a total phase then results over the length of a green phase and a red phase. In order to determine the probability of reaching the traffic light at green, the duration of the green phase is divided by the duration of a complete traffic light. Subsequently, the expectation value can be formed with a 100-time passing.

This approach leads to a theoretical solution which, however, should be questioned critically. The result as well as the randomness of the arrival can be influenced depending on the traffic light circuit and any traffic lights which have been traversed previously. However, the problem is a successful application of the probability calculation in everyday life and can be used with the first elaborations of the probability concept.

Date: 26. June 2017 | By: Simone Jablonski | Category:  | No Comments

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