2--But what does a thumb have to do with rules? Rule of Thumb
 
1--I thought you were supposed to be in Mexico City for your friend's wedding.
 
2--Yeah...about that... I missed my flight last night.
 
1--I thought getting there 40 minutes early would be enough time, but it wasn't.
 
2--For international flights, the rule of thumb is to get to the airport two or even three hours early.
 
1--Unfortunately, your advice comes about ten hours too late, Jonathan.
 
2--A "rule of thumb" is a general estimate.
 
1--It is not scientific or exact.
 
2--This expression comes from using body parts as units of measure.
 
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注解：
 
1.thumb翻阅
2.flight航班
3.measure测量

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译文：

1--拇指是你手掌上最短的一个手指。
2--不过一个拇指和规则有什么关系？经验法则
1--我记得你应该是去墨西哥城参加你朋友的婚礼啊。
2--是的，不过我错过了昨晚的航班。
1--我本以为提前40分钟到时间完全够了，但是还是没来得及。
2--对国际航班来说，经验法则是要提前两个甚至三个小时到机场。
1--很不走运，你的忠告迟到了大约10个小时，Jonathan。
2--一则经验法则是一种大致的估计。
1--它并不是科学的或者说确切的。
2--这个短语来源于用身体部位作为衡量的单位。