Print a manuscript, if you type 70 words per minute, you can finish typing in 4 hours. If you type 80 characters per minute, how many hours can you finish typing? (Solution with proportional knowledge)
打印一份稿件，如果每分钟打70个字，4小时可以打完．如果每分钟打80个字，几小时可以打完？(用比例知识解)
<gadget id="calculator">60 * 4 * 70</gadget>
<output>16_800</output>

<gadget id="calculator">80 * 60</gadget>
<output>4_800</output>

<gadget id="calculator">16_800 / 4_800</gadget>
<output>7/2 = around 3.5</output>

<result>7/2 = around 3.5</result>