There are 31 days in May.

五月份有31天。

《牛津词典》

The park is open from 1 May to 31 October.

公园从5月1日到10月31日开放。

《牛津词典》

He called from Washington, having been there for 31 hours straight.

他从华盛顿打来了电话，他已在那里连续呆了31个小时了。

《柯林斯英汉双解大词典》

"It is already in the hands of 1.2 million children, in 31 countries,19 languages.

VOA: special.2010.04.12

And what we find out is the wavelength of a Matsuzaka fastball is 1.1 times 10 to the -31 meters.

我们算出松阪快球的波长,是1，1乘以10的负31次方米。

麻省理工公开课 - 化学原理课程节选

So 1.1 times 10 to the -31 meters is not, in fact, a significant number when we're comparing it, for example, to the length of a ball, or the size of the baseball field.

所以1，1乘以10的负31次方米，事实上并不是一个很重要的数字，举例来说，当它与一个球的长度，或者一块棒球场地对比时。

麻省理工公开课 - 化学原理课程节选