Teacher Zhang's original salary was 1,500 yuan, but recently he was promoted to a senior title, and his salary rose to 2,100 yuan. What percentage has Mr. Zhang's salary increased?
张老师原来的工资是1500元，最近他晋升了高级职称，工资涨到了2100元．张老师的工资涨了百分之几？
<gadget id="calculator">2_100 - 1_500</gadget>
<output>600</output>

<gadget id="calculator">600 / 1_500</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>