Question

what number is missing ?
27, 54 ,?, 108, 135, 162, 189, 216.

Answer 1

54 - 27 = 27

135 - 108 = 27

162 - 135 = 27

189 - 162 = 27

216 - 189 = 27

So,

Missing number = 54 + 27

81..................

Answer 2

I know 81 ok
27,54,81,108,135,162,189,216