In the science experiment class, Chen Chen wants to adjust 300 grams of salt water with a concentration of 15% to a salt water with a concentration of 40%. If the method of adding salt is used, how many grams of salt can be added?
科学实验课上，陈辰要把300克浓度为15%的盐水调成浓度为40%的盐水，如果用加盐的方法，可以加多少克盐？
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">300 * (3/20)</gadget>
<output>45</output>

<gadget id="calculator">300 - 45</gadget>
<output>255</output>

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

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">255 / (3/5)</gadget>
<output>425</output>

<gadget id="calculator">425 - 300</gadget>
<output>125</output>

<result>125</result>