Final answer:
To convert 81 µg of aspirin to nanograms, multiply by 1000. The result is 81000 ng, or 8.1 x 10⁴ ng, which is option (d).
Step-by-step explanation:
The question states that a low-dose aspirin tablet contains 81 µg (micrograms) of aspirin and asks how many ng (nanograms) of aspirin are in the tablet. To convert micrograms to nanograms, we need to know that 1 µg is equal to 1000 ng. Therefore, we multiply the number of micrograms by 1000 to get the number of nanograms.
81 µg of aspirin × 1000 ng/µg = 81000 ng of aspirin.
This means that the correct answer is: 8.1 x 10⁴ ng of aspirin which corresponds to option (d) in the question.