Challenge Your Brain With Real-Time Math Battles for Grown-Ups

Adults returning to arithmetic are usually not missing knowledge — they are missing speed, because the facts have not been retrieved in twenty years and have gone from recall back to reconstruction. The route back is short: the facts are still there and rebuild much faster than they were first learned. Most people notice a difference within a fortnight of daily minutes.

Mixed practice is harder than it looks, and usefully so. When every question is addition, a child can switch off and apply one procedure; when the operation changes each round, they have to read the problem first. That reading step is exactly what breaks down in word problems and on tests, so drilling it deliberately is worth the extra difficulty.