Here is a point that can be confusing, even for native English speakers. Take a look at this example sentence:
- I can cook dinner in twenty minutes.
This sentence actually has two meanings, because we use in + a time period two different ways. Let’s look at this grammar today.
You can use in + a time period to talk about a future point in time.
- I can cook dinner in twenty minutes. This means, twenty minutes from now, I can begin cooking dinner.
- I am going on vacation in one month. One month from today, I am going on vacation.
- Jack said he will be here in an hour. Jack will arrive one hour later.
You can use in + a time period to talk about the amount of time that is required to do something. In this case, in + a time period means within. When we use in + a time period with this meaning, we generally do so when we talk about ability.
- I can cook dinner in twenty minutes. This means, within twenty minutes, I can cook dinner. In other words, I am a pretty quick chef!
- I usually reach my office in 45 minutes. My commuting time is 45 minutes.
- I can finish the report in about two hours. I only need two hours to complete the report.
Can you cook a mean in 20 minutes? Can you reach your school or office in 30 minutes?