In the third grade mathematics, there are four for nine dollars, how many for six dollars, 9/4=2.25, 6/2.25 = 2.66667, and only two for six dollars, but less than three. So in the third grade, there were 4 in 9 yuan and 2.7 in 6 yuan. In a word, this is a very simple elementary school math problem. I hope you study hard and master knowledge. Learn to draw inferences from others, and you will solve similar problems in the future.