If the multiplicand increases by 15 and the multiplier remains unchanged, the product increases by 180; if the multiplicand remains unchanged and the multiplier increases by 4, the product increases by 120. What is the product of multiplying the two numbers together?
如果被乘数增加15，乘数不变，积就增加180；如果被乘数不变，乘数增加4，那么积就增加120．原来两个数相乘的积是多少？
<gadget id="calculator">120 / 4</gadget>
<output>30</output>

<gadget id="calculator">180 / 15</gadget>
<output>12</output>

<gadget id="calculator">30 * 12</gadget>
<output>360</output>

<result>360</result>