The mother is 40 years old, the son's age is the mother's (2/5), and it happens to be the grandmother's age (1/4). How old is grandma?
妈妈今年40岁，儿子的年龄是妈妈的(2/5)，又正好是外婆年龄的(1/4)．外婆今年几岁？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(2/5) / (1/4)</gadget>
<output>8/5 = around 1.6</output>

<gadget id="calculator">40 * (8/5)</gadget>
<output>64</output>

<result>64</result>