Mix 10 kg of brine with a salt content of 45% and 20 kg of brine with a salt content of 30%, what is the salt content of the brine?
把含盐率是45%的盐水10千克和含盐率是30%的盐水20千克混合在一起，盐水的含盐率是多少．
<gadget id="calculator">45 / 100</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">10 * (9/20)</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">20 * (3/10)</gadget>
<output>6</output>

<gadget id="calculator">(9/2) + 6</gadget>
<output>21/2 = around 10.5</output>

<gadget id="calculator">10 + 20</gadget>
<output>30</output>

<gadget id="calculator">(21/2) / 30</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">(7/20) * 1</gadget>
<output>7/20 = around 0.35</output>

<result>7/20 = around 0.35</result>