Master Li wants to process a batch of parts. The ratio of the number of parts processed on the first day to the total number of remaining parts is 1:3. If another 150 parts are processed, half of this batch of parts can be completed. How many parts are there in total?
李师傅要加工一批零件，第一天加工的零件个数与剩下零件总数的比是1：3，如果再加工150个零件就可以完成这批零件的一半．这批零件一共有多少个？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

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

<gadget id="calculator">(2/3) - (1/2)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">150 / (1/6)</gadget>
<output>900</output>

<result>900</result>