Final answer:
To determine how long something has been going on or in use, you can use methods such as starting and stopping a stopwatch or using the R/P ratio to calculate the timescale of resource availability.
Step-by-step explanation:
In order to determine how long something has been going on or in use, you can use various methods depending on the situation. If you have access to the event, you can start a stopwatch or timer at the beginning and stop it at the end to measure the elapsed time. For example, if you observe a light turning from green to red, you can start the timer and stop it when the light turns red. Another method is to use the R/P ratio, which stands for reserves to production, to calculate the timescale of resource availability.
For example, if you have $10,000 in a bank account and spend $1,000 per month, you can estimate that you will be able to go for ten months without additional income. Similarly, if you have an estimate of the remaining resource in the ground and the current rate of use, you can divide to get the timescale.
Overall, the method used to measure how long something has been going on or in use depends on the specific scenario and resources available for measurement.