- I am planning to do it in the next ten minutes.
- I am planning to do it for the next ten minutes.
Do the two sentences mean the same thing? I am sure using for is correct, but I want to know whether using in changes the meaning.
No, they don't necessarily mean the same thing.
I'm planning to do it in the next 10 minutes.
suggests that you will do something that will probably take much less than 10 minutes to complete, e.g., throw out the garbage.
I'm planning to do it for the next 10 minutes.
means that you will spend the next 10 minutes doing something, e.g., exercising or practicing your guitar or doing your homework.
Grammatically, both are correct. Semantically, however, they are different.
It's a question of duration in this case.
The first example means that you are going to start and possibly complete "it" sometime in the next ten minutes. You could start three minutes from now and finish seven minutes from now.
The second example means that you are going to do the action for the entire duration of the next ten minutes.