My study permit says I can work 20 hours per week. Can I work more hours one week and fewer hours the next one?

The rationale behind the 20 hours is that the students can keep their programs in good standing while they are able to earn some extra income. The government has been very specific about the 20-hours maximum to work and there is no regulation that allows interchanging the number of hours or doing add-ups.

Also, read this article on International Students in Canada working 20 hours a week.