A typist has to type a manuscript of 40 pages. She has typed 30 pages of the manuscript. What is the ratio of the number of pages typed to the number of pages left?
Total pages of manuscript to type = 40
Total typed pages = 30
Total left pages = 40 – 30 = 10
Ratio of the number of pages typed to the number of pages left = 
Ratio = 3:1
75