Tashi reads a 150-page technical book and finishes 20% of it in the first 3 days. According to this calculation, how many days will it take to finish reading this book?
扎西读一本150页的科技书，头3天读完20%，照这样计算，读完这本书一共需要几天？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / (1/5)</gadget>
<output>5</output>

<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<result>15</result>