mean length的用法和樣例：
例句
- If this joint length ratio is greater than 10, the rock is likely to be blocky.
採用切割法找到所有組成岩體的任何塊體，基於裂隙的平均長度與平均間距，引進產生三維裂隙多邊形的統計方法。 - Typically, most music videos run for about 3 to 4 minutes, the average length of a pop song.
絕大多數的音樂錄影帶只播放三到四分鐘，基本上是流行歌曲的平均長度。
