25% of the number A is exactly the number B. If the number B is 210, what is the number A?
甲数的25%正好是乙数的，如果乙数是210，那么甲数是多少？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">210 / (1/4)</gadget>
<output>840</output>

<result>840</result>