Given that 2a=5b, only ((a)/(b))= how many of the following ratios are correct.
已知2a=5b，下列比例式只有((a)/(b))=多少是正确的．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / (2/5)</gadget>
<output>5/2 = around 2.5</output>

<result>5/2 = around 2.5</result>