Performing math in your head requires concentration and a working memory. These improve with practice and are useful for more than just math (like following complex writing or multiparty discussions).
With computers, people won't perform the basic calculations in their head. But their strategy-forming about what, of the gigantic possibility space, they could or should ask the computer next will still require the same old concentration and working memory... and more.
With computers, people won't perform the basic calculations in their head. But their strategy-forming about what, of the gigantic possibility space, they could or should ask the computer next will still require the same old concentration and working memory... and more.