Final answer:
To calculate the number of grains of medication the patient received, multiply the number of tablets by the amount of medication in each tablet.
Step-by-step explanation:
To calculate the number of grains of medication the patient received, we need to multiply the number of tablets (3) by the amount of medication in each tablet (1/120 of a grain).
So, the patient received 3 * (1/120) = 1/40 of a grain of medication.
Therefore, the patient received 1/40 of a grain of medication.