'Mathemagics' https://www.amazon.co.uk/Mathemagics-Genius-without-Really-Trying/dp/0737300086 https://www.amazon.co.uk/Mathemagics-Genius-without-Really-T...

'Mathemagics' https://www.amazon.co.uk/Mathemagics-Genius-without-Really-Trying/dp/0737300086 https://www.amazon.co.uk/Mathemagics-Genius-without-Really-T... This is awesome book, it teach you all sort of tricks from 3 digits addition to 3 digits multiplication. I know its written for school teens, but still pretty helpful life skills.