Challenges may appear and disappear depending on what our system knows about your math knowledge. If you don’t have any challenges available on your learning dashboard, we recommend completing practice tasks. As you practice these skills and make more progress through your mission, we’ll generate your next challenge. Mastery challenges are usually only offered for tasks which are at the "practiced" level and above.
Additionally, our system spaces out mastery challenges to help you retain all the new skills you’re learning. Research suggests that skills are learned best when they're practiced repeatedly over several days. For this reason, you’ll sometimes see a timer indicating when your next mastery challenge will be available. The 16 hour waiting period is not an arbitrary choice, but one selected to maximize the benefit of exercise for most students. When you come back and complete this mastery challenge, you’ll have the chance to level up on skills.