A certain electric fan used to be 150 yuan per unit, but now it is reduced to 120 yuan per unit. How much is the price reduction? Column: how much.
某种电扇原来每台150元，现在降低到每台120元，降价百分之几？列式：多少．
<gadget id="calculator">150 - 120</gadget>
<output>30</output>

<gadget id="calculator">30 / 150</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>