The guest house has a new group of guests. For 2 people per room, 15 rooms are needed. How many rooms are needed if there are 3 people in each room?
招待所新来一批客人．每间住2人，需要15间房．如果每间房住3人，需要几间房？
<gadget id="calculator">15 / 3</gadget>
<output>5</output>

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

<result>10</result>