New posts in Mental Arithmetic

How to find a volume of this figure (which is $3080 \text{ cm}^3$) in a few seconds?

(Quickly) finding the smallest fraction

How can I easily double any size number in my head?

Did Feynman mentally compute $\sqrt[3]{1729.03}$ by linear approximation?

How do people perform mental arithmetic for complicated expressions?

Mental Math: Finding Square Roots to 1 Decimal Point

What is the fastest way to multiply two digit numbers?

Books, sites, guides about mental arithmetic by hand and tricks?