There is 60 kilograms of 30% salt water, and after evaporating some water, the concentration becomes 40%, so how many kilograms is the total weight at this time?
有30%的盐水60千克，将它蒸发掉一些水分之后浓度变为了40%，那么此时总重还有多少千克．
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(3/10) / (2/5)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">60 * (3/4)</gadget>
<output>45</output>

<result>45</result>