A normal saline solution weighs 250 grams and has a salt content of 10%. If the salt content is increased to 25%, how many grams of salt should be added?
一种生理盐水重250克，含盐率是10%，现在使含盐率提高到25%，应加入多少克盐．
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(9/10) / (3/4)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">250 * (6/5)</gadget>
<output>300</output>

<gadget id="calculator">300 - 250</gadget>
<output>50</output>

<result>50</result>