The packaging of a medicine bottle reads: 90 tablets, 10 grams each. The prescription written by the doctor said: eat 3 times a day, 20 grams each time. How many days can this bottle of medicine be taken according to the doctor's prescription?
一种药瓶的包装上写着：90片，每片10克．医生开的处方上写着：每天吃3次，每次20克．这瓶药按医生的处方，可以吃多少天？
<gadget id="calculator">3 * 20</gadget>
<output>60</output>

<gadget id="calculator">10 / 60</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">90 * (1/6)</gadget>
<output>15</output>

<result>15</result>