If 2 is added to the former term of 1:5, how much should the latter term be increased to keep its ratio constant.
如果在1：5的前项加上2，要使它的比值不变，后项应增加多少．
<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">3 / 1</gadget>
<output>3</output>

<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<gadget id="calculator">15 - 5</gadget>
<output>10</output>

<result>10</result>