number average molecular weight

例句：

1. 1. Thenumber of students in the class is 30.
   班上的学生有30个。
2. 2.The number of cars on the road has doubled since last year.
   路上的汽车数量从去年增加了一倍。
3. 3. The number of people who have signed up for the event is increasing daily.
   报名参加该活动的人数每天都在增加。
4. 1. The average temperature for this month is 15 degrees Celsius.
   这个月的平均温度是15摄氏度。
5. 2. The average lifespan of a human being is about 75 years.
   人类的平均寿命大约是75年。
6. 3. The average income for a software engineer is around $60,000 per year.
   软件工程师的平均年收入约为6万美元。