Fractions strategies

Question

What is the missing fraction:

1/12, 1/27, 1/6, 1/9, ? , 1/3

Answer 1

1/12, 1/27, 1/6, 1/9, ?, 1/3

1st, 3rd, 5th are 1/12, 1/6, 1/3 have denominators each half the preceding

then

alternative sequence is

2nd, 4th, 6th, 1/27, 1/9, 1/3 where denominators are 1/3 the previous term

so

the full sequence is

1/12, 1/27, 1/6, 1/9, 1/3, 1/3, 1/(3/2), 1/(3/3), ... or 1/12, 1/27, 1/6, 1/9, 1/3, 1/3, 2/3, 1, ...

missing term is 1/3