CAMBRIDGE LEARNER'S DICTIONARY, heavy:
Oxygen is sixteen times heavier than hydrogen.
Could we say
'Oxygen is fifteen times heavier than hydrogen.'
without changing its original meaning (as we Chinese would always think)?
Thank you very much.
I'm not sure if I understand your question, but you can't change sixteen to fifteen without changing the meaning. Sixteen and fifteen are not the same.
The second statement is fine grammatically.