In the multiplication formula, if one factor is expanded to 4 times the original factor and the other factor is reduced to the original (1/5), then the product is reduced to the original value
在乘法算式里，一个因数扩大为原来的4倍，另一个因数缩小为原来的(1/5)，则积缩小为原来的多少
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">4 * (1/5)</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>