How to apply the 85% rule

Imagine you're studying for a test by doing practice problems.

• An easy way to solve the problems would be with an open book and worked examples.
• The most difficult would be to work on novel problems with the book closed.

The 85% rule suggests that learning is best when we practice tasks that we can succeed at roughly four-fifths of the time. If you're getting one out of every five problems wrong, you may need extra help. If you're getting nearly all the problems right, you need to move to more difficult ones.