If 0 < x < 1, is it possible to write x as a terminating decimal?
(1) 24x is an integer.
(2) 28x is an integer.
The Manhattanprep official answer is "Both statements TOGETHER are sufficient, but NEITHER one ALONE is sufficient." However, I believe "EACH statement ALONE is sufficient." Manhattanprep's explained its answer by giving the example: if x is 1/2, 24x = 12, and the decimal terminates (0.5). If, however, x = 1/3, 24x = 8, but the decimal does not terminate (0.3333….).
This example actually makes statement (1) sufficient, as now we know that it is "possible to write x as a terminating decimal". With statement (2), we can also know that it is possible to write x as a terminating decimal, just as proofed by Manhattenprep's example, when 28x=14, x will equal to 0.5, which is a terminating decimal. Hence, knowing that 28x is an integer, we can be sure that it is possible to write x as a terminating decimal.
If the question were changed to "If 0 < x < 1, is x a terminating decimal?", with the same premises (statements), then the official answer "both statement TOGETHER are sufficient,..." would be the correct answer.