Maths Chest - National STEM Centre:
If you create a free login, you can access the pdf versions of the student workbooks and teacher answer keys for basic math practice skills. These books were published in the 80's and focused on game based practice with the idea that if math was fun, students would have an easier time learning it. You can download levels 1-7 for free once you create a login. As these were published in the UK, these do not correlate exactly to US grade levels - check ages / math skills covered to find appropriate materials for your grade level.
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