The ratio of the number of red, yellow and blue glass balls is 1:2:3. If there are 6 red balls, how many blue balls are there?
红、黄、蓝三种颜色的玻璃球数量的比是1：2：3，如果有6个红球，那么，蓝色球有多少个．
<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<result>18</result>