How many kilograms of water should be evaporated to produce 40% salt water by evaporating water from 200 kg of salt water with 10% salt content?
要从含盐10%的200千克盐水中蒸发水分制成含盐40%的盐水，应蒸发掉多少千克水分？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">200 * (2/5)</gadget>
<output>80</output>

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

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

<gadget id="calculator">80 - 20</gadget>
<output>60</output>

<gadget id="calculator">60 / (2/5)</gadget>
<output>150</output>

<result>150</result>