Question

a=18.9,d=2.5,n=?,an=3.6

Answer 1

a n = 3.6

a + (n - 1) d = 3.6

-18.9 + (n - 1) (2.5) = 3.6

(n -1) 2.5 = 3.6 + 18.9

(n - 1) 2.5 = 22.5

 n - 1 = 22.5/2.5

  n - 1 = 9

  n = 9 + 1

  n = 10