Given a ratio, its latter term is 1.5, and the ratio is 3, then what is the former term of the ratio.
已知一个比，它的后项是1.5，比值是3，那么比的前项是多少．
<gadget id="calculator">1.5 * 3</gadget>
<output>4.5</output>

<result>4.5</result>