Instructions and reasons

Since the COVID-19 outbreak, I’ve been hearing a lot that you should wash your hands for at least 20 seconds. Washing my hands makes sense, sure, because of germs, but why 20 seconds? There’s probably a reason, but I haven’t heard it yet. Why is 20 seconds better than 10 seconds? Are you supposed to wash every part of your hands twice? If so, why don’t they just say that? Is 10 seconds half as good, 90% as good, or no good at all compared to 20 seconds? Does the magic happen at 15 seconds and they just want you to play it safe in case we count too fast? I don’t know. Because no one told me. 

If you want someone to do something and you give them instructions, be sure to give them the reasons for the instructions too. 

Instructions: Don’t jump on the table.

Instructions with a reason: Don’t jump on the table because it might break.