Beyond Trachtenberg

This book has a lot of useful information related to calculation, from tricks to multiply by the first natural numbers without the need of a calculator to methods to raise a number to any other, or to calculate by hand the nth root of a number or its logarithm, passing through uncommon curious ways of multiplying and dividing, the detection of errors in the operations, the decomposition in factors of the first 1000 numbers (highlighting among them those that are prime), the simplification of fractions, rules to determine the significant figures of a number and its rounding and a cursory look at the ABN method that complements traditional education.