A vegetable vendor buys 200 yuan of tomatoes from the vegetable market, and if he sells all of them at 1.4 yuan per kilogram, he can earn 40%. Due to climate factors, except some of the good quality sold at 1.4 yuan per kilogram, the rest were sold at 1 yuan per kilogram, so in fact only 10% of the profit was made. Q: How many kilograms of them are sold at 1.4 yuan per kilogram.
一菜贩从菜市场购进200元的西红柿，如果全部以每千克1.4元卖出，可以赚四成．由于气候因素，除了一部分质量好的以每千克1.4元卖出外，其余的是以每千克1元卖出的，所以实际上只赚了一成．问：其中多少千克是按每千克1.4元卖出的．
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 + (2/5)</gadget>
<output>7/5 = around 1.4</output>

<gadget id="calculator">(7/5) / 1.4</gadget>
<output>1</output>

<gadget id="calculator">200 * 1</gadget>
<output>200</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">200 * 1 * (1/10)</gadget>
<output>20</output>

<gadget id="calculator">20 - 200</gadget>
<output>-180</output>

<gadget id="calculator">200 + (-180)</gadget>
<output>20</output>

<gadget id="calculator">1.4 - 1</gadget>
<output>0.4</output>

<gadget id="calculator">20 / 0.4</gadget>
<output>50</output>

<result>50</result>