该群体的平均年龄是20岁。

The ___average age of the group is 20 years.

这座山上的天气非常好，平均温度为17摄氏度。

The weather on this mountain is fantastic, with an ___average temperature of 17°C.

通过求和并除以数量来计算平均值。

Calculate the ___average by summing the numbers and dividing by the count.