Adjective
astute - Ability to understand things quickly and clearly, and to use the knowledge well
From a very early age, Gail instinctively knew everything about business, and and after college she proved to be an astute business woman, and became a millionaire before the age of 30.
frazzled - To feel completely exhausted and worn out, and unable to think straight, after a great deal of mental or physical effort
After being up two nights in a row writing a 60 page history paper, and drinking 60 cups of coffee, Simon's mind felt frazzled.