A pasture grows grass at the same rate every day. This pasture can feed 14 cows for 30 days, or 70 sheep for 16 days. If 4 sheep eat as much grass as 1 cow. Then how many days can 17 cows and 20 sheep eat the grass on this pasture?
一片牧场，每天生长草的速度相同．这片牧场可供14头牛吃30天，或者可供70只羊吃16天．如果4头羊的吃草量相当于1头牛的吃草量．那么17头牛和20只羊一起吃这片牧场上的草，可以吃多少天？
<gadget id="calculator">14 * 30</gadget>
<output>420</output>

<gadget id="calculator">70 / 4</gadget>
<output>35/2 = around 17.5</output>

<gadget id="calculator">(35/2) * 16</gadget>
<output>280</output>

<gadget id="calculator">420 - 280</gadget>
<output>140</output>

<gadget id="calculator">30 - 16</gadget>
<output>14</output>

<gadget id="calculator">140 / 14</gadget>
<output>10</output>

<gadget id="calculator">30 * 10</gadget>
<output>300</output>

<gadget id="calculator">420 - 300</gadget>
<output>120</output>

<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">5 - 10</gadget>
<output>-5</output>

<gadget id="calculator">17 + (-5)</gadget>
<output>12</output>

<gadget id="calculator">120 / 12</gadget>
<output>10</output>

<result>10</result>