For every 1.2m railway, 2 sleepers are needed, and how many sleepers are needed to lay a 6 km long railway.
每铺铁路1.2米，需2根枕木，铺一段长6千米的铁路，需多少根枕木．
<gadget id="calculator">6 * 1_000</gadget>
<output>6_000</output>

<gadget id="calculator">6_000 / 1.2</gadget>
<output>5_000</output>

<gadget id="calculator">5_000 * 2</gadget>
<output>10_000</output>

<result>10_000</result>