To produce a batch of parts, first A alone will do 3 hours to complete (1/6) of the total number, and then A and B will work together for 2 hours to complete (4/9) of the total number. It is known that B can make 70 parts per hour How many parts are there in total?
要生产一批零件，先由甲独做3小时，完成总数的(1/6)，接着甲和乙合做2小时，又完成总数的(4/9)，已知乙每小时能做70个零件，这批零件共有多少个？
<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">(4/9) / 2</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/6) / 3</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">(2/9) - (1/18)</gadget>
<output>1/6 = around 0.166667</output>

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

<gadget id="calculator">70 * 6</gadget>
<output>420</output>

<result>420</result>