Question

How long for a good presentation​

Answer 1

should at least last 8-9 mins maximum

Step-by-step explanation:

the audience might not understand if it is shorter than 7 mins

the audience might get bored if it is very long

Answer 2

A good presentation must at least be 7-10 minutes long and probably not exceed a certain point where the presentation get's boring.

For example in a school project, it shouldn't exceed 15 minutes because there are other students needing to present. In a business proposal however, can be 30 minutes long or more just to stick with the subject and good points.