The ratio of boys to girls in mr. Chens class is 4 to 5. Which of the following cannot be the total number of students in mr. Chens class: 18,20,27, or 36
It would be 20, because 5 plus 4 is 9 and you can multiply 9 by 2 to get 18, 9 by 3 to get 27, and 9 by 4 to get 36, but you can't multiply anything by 9 to get to 20.
