Master Zhang used to take 3 hours to produce 150 parts, but now it is reduced to 2 hours. How much per hour has the work efficiency increased?
张师傅过去生产150个零件需要3小时，现在减少到2小时，每小时工作效率提高了百分之几？
<gadget id="calculator">150 / 2</gadget>
<output>75</output>

<gadget id="calculator">150 / 3</gadget>
<output>50</output>

<gadget id="calculator">75 - 50</gadget>
<output>25</output>

<gadget id="calculator">25 / 50</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>