A story book, 15 pages per hour, 6 hours to finish. If you read 10 pages per hour, how many hours can you finish it? (Solve with ratio)
一本故事书，每小时看15页，6小时看完．如果每小时看10页，几小时可以看完？(用比例解)
<gadget id="calculator">15 * 6</gadget>
<output>90</output>

<gadget id="calculator">90 / 10</gadget>
<output>9</output>

<result>9</result>