Explanation:
3/2 9/8 27/32 81/128
so we see that the numerator value starts with 3 and is then always multiplied by 3.
and the denominator value starts with 2 and is then always multiplied by 4.
so, the factor of one term to the next is simply 3/4.
3/2 × 3/4 = 9/8
9/8 × 3/4 = 27/32
27/32 × 3/4 = 81/128