There is 30 kg of salt water with a salt content of 15%. According to the need, to make the salt content of the salt water 10%, how much water can we add?
有含盐率为15%的盐水30千克，根据需要，要使盐水的含盐率变为10%，那么，我们可以加水多少千克．
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

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

<gadget id="calculator">(3/20) / (1/10)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">30 * (3/2)</gadget>
<output>45</output>

<gadget id="calculator">45 - 30</gadget>
<output>15</output>

<result>15</result>