Answer:
15 students
Explanation:
% of students attended reunion in 2005 = 87.5% of 120
no of students attended reunion in 2005 = 87.5/100 * 120 = 105.
no of students attended reunion in 2006 = 90
no of students attended reunion in 2007 = 75
So , the series for the given year is
105, 90, 75
we can see that this arithmetical progression series
in arithmetical progression series
common difference is = nth term - (n-1)th term
lets takes 3rd and second term as nth term and (n-1)th term
common difference(d) is =75 - 90 = -15
n th term for any arithmetical progression series is given by
nth term = a + (n-1) d
where a is the first term
n is the nth term
d is the common difference
we have to calculate number of students in reunion of of 2010
as reunion began from 2005
2005,2006,2007,2008,2009,2010
so, 2010 is 6th term in series of 105, 90, 75....
6th term = a + (n-1) d
a is 90
6th term = 90+ (6-1)* -15
6th term = 90+ (5)* -15 = 90 - 75 = 15.
Thus, 15 students will attend reunion of 2010