Question

Jumlah kelipatan 3 antara bilangan 100-300?

Answer 1

a = 102
b = 3
Un = 297

Un =a + (n-1)b
297 = 102 + (n-1)3
297 = 102 + 3n – 3
297 = 99 + 3n
297-99 = 3n
198 = 3n
  = n
   66 = n

Sn = (2a + (n-1)b )
S66 = (2 x 102 + ( 66-1)3)
       = 33 ( 204 + 195 )
       = 33 ( 399 )
       = 13167