That's the average of all of your weekly quizzes in the recitation. Each of those three monthly tests gives also a sixth.

就是你们每周背诵课的测试的平均分,而三次的月考,的成绩也占六分之一。

麻省理工公开课 - 固态化学导论课程节选

In addition to the weekly homeworks, there will be monthly tests.

除了每周的家庭作业，每个月还会有月考。

麻省理工公开课 - 固态化学导论课程节选