There is a set of gears that mesh with each other. The large gear rotates 80 revolutions per minute, which is 4/5 less than the revolutions per minute of the small gear. How many revolutions does the pinion make per minute?
有一组相互咬合的齿轮．大齿轮每分钟转80周，比小齿轮每分钟转动的周数少(4/5)．小齿轮每分钟转多少周？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">80 / (1/5)</gadget>
<output>400</output>

<result>400</result>