If the weight of paper is reduced from 38 to 30, it will reduce 2400 words. According to relevant information: As the total number of words in the paper is 8000 words, the duplicate checking rate is 30%, that is, the repetition rate is 30%. Then the number of repeated words is: 8000x30%=8000x0.3=2400, that is, the duplicate checking rate of 8000-word papers is 2400 words. Therefore, if the number of papers is reduced from 38 to 30, it will be reduced by 2400 words.