In multiplication, if one factor is multiplied by 4 and the other factor is multiplied by 5, how many times the product will be multiplied.
在乘法里，一个因数扩大4倍，另一个因数扩大5倍，积扩大多少倍．
<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<result>20</result>