Question

determine quantos muktiplos de 4 existem entre 15 e 90

Answer 1

16,20,24,28,32,36,40,44,48,52,56,60,64,68,72,76,80,84,88.

Answer 2

15 e 90
r = 4
a 1 = 16
a n = 88
a n = a 1 + (n - 1 ) .r
88 = 16  + (n - 1 ).4
88 - 16 = 4 n - 4 
72= 4 n - 4
4 n - 4 = 72
4 n = 72 + 4
4 n = 76
n = 76/4
n = 19
Existem 19 múltiplos de 4 entre 15 e 90