The master and the apprentice produce the same part. The apprentice (1/4) produces 20 pieces in an hour, the master produces 120 pieces in an hour, and the two work together to produce 150 pieces. How many hours will it take?
师傅和徒弟生产同一种零件，徒弟(1/4)小时生产了20个，师傅每小时生产120个，两人共同生产150个，需要多少小时？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">20 / (1/4)</gadget>
<output>80</output>

<gadget id="calculator">80 + 120</gadget>
<output>200</output>

<gadget id="calculator">150 / 200</gadget>
<output>3/4 = around 0.75</output>

<result>3/4 = around 0.75</result>