There are two groups of students in the sixth grade. There are 45 students in group A, and 55 students in group B. If, on a particular day, 20% of the students in group A forget their homework, and 40% of the students in group B forget their homework, then what percentage of the sixth graders forgot their homework?	Choose the correct option
A) 23 %	B) 25 %	C) 29 %	D) 31 %	E) 36 %

Rationale: "number of students in group a = 45 students who forget homework in group a = 20 % of 45 = 9 students number of students in group b = 55 students who forget homework in group b = 40 % of 55 = 22 students total number of students = 45 + 55 = 100 students who forgot homework = 9 + 22 = 31 students percentage of students who forget homework = 31 / 100 * 100 = 31 % answer : d"
Answer: D