If the student population began with 100 students, it was 180 by the end of the full 20 year period.
Because a:b is 1:3, we divide the 80 additional students into group a, 20, and group b, 60. When 20 students were added the first ten years, it represented 20% of 100. When 60 students were added during the second period, it represented 50 percent of 120.
The answer is C.
Carcass wrote:
The student population of a certain school increased a% from 1995 to 2005 and b% from 2005 to 2015. If the student population increased by 80% from 1995 to 2015 and the increase in the number of students in the second decade was three times the increase in the number of students in the first decade, what is the value of b?
A. 20
B. \(26 \frac{2}{3}\)
C. 50
D. 60
E. 75