Complete the series: 69, 73, 75, 81, 85, ........

93

69, 73, 75, 81, 85, ........

i)   69 + 4 = 73 ,   ii)   73 +  2 = 75

             ⇓                             ⇓

iii) 75 + 6 = 81,     iv)  81 + 4 = 85

             ⇓

v) 85 + 8 = 93, ..............................      

Thus, the series is as follows: +4, +2, +6, +4, +8, +6 and so on...

Therefore,  next number will be 85 + 8 = 93