Today I am going to share the homework correction quoted from my JLPT N4 course!
The student’s sentence is not correct. Can you find the mistake?

 

[Student’s sentence]

私はサンドイッチを20分に作れます。

*わたしはさんどいっちをにじゅっぷんにつくれます。

 

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[My correction]

私はサンドイッチを20分に作れます。
→私はサンドイッチを20分で作れます。
I can make a sandwich in 20 minutes.

 

[Duration＋で] refers to the amount of time used to complete some task.
The time you spend making the sandwich is twenty minutes, so で marks that duration.

e.g.
スミスさんは３日でそのレポートを書(か)きました。
Smith-san took three days to write that report.

あと1時間(じかん)で仕事(しごと)が終(お)わります。
I will finish my work in one hour.

 

I hope my explanation helps you. 😊

 

In the JLPT course, all lessons come with homework, if you submit your homework, I will reply with corrections.
I can break down the Japanese grammar and point out mistakes, explaining the structure and nuances of Japanese in an easy-to-understand way.
You can also ask me any questions as much as you want. I will teach you until you get it!