Mr. Li typed 200 words in 4 minutes. At this speed, how long does it take for him to type an article of 1800 words?

Mr. Li typed 200 words in 4 minutes. At this speed, how long does it take for him to type an article of 1800 words?

If you type 200 words in 4 minutes, you can type 50 words in 5 minutes!
1800 divided by 50 is 36 minutes!
If you remove the 200 words you have typed, there are still 1600 words left
1600 divided by 50 is 32 minutes~
Hope to help you