Lecciones de matemáticas del oficio

The drills on this site mark your answers; these pages teach the method first. Each lesson is the same shape — why the arithmetic is the way it is, three examples worked all the way through, the matching drill embedded so you can try it on the spot, and a button that prints twenty fresh questions with an answer key for a class or a lunch break. None of it is a lookup: it is all arithmetic you can reason out, which is exactly why it is worth being quick at.

• Las fracciones en una cinta

  Why a tape is in sixteenths, how to reduce, and how to add two marks without a calculator.

  1Adding fractions drillPrint 20

• Leer una cinta rápido

  Tick lengths, the nearest-long-mark trick, and the habit that stops you miscounting sixteenths.

  2Prueba de cinta métricaPrint 20

• Triángulos rectángulos en la obra

  3-4-5 for squaring a layout, Pythagoras for the travel of an offset, and where the multipliers come from.

  3Right-triangle drillPrint 20

• Metric ↔ imperial without a calculator

  25.4 to the inch, 0.3048 to the foot, the rough versions you can do in your head, and when rough is not good enough.

  4Conversion drillPrint 20

• Los porcentajes en el oficio

  Percent of a number, what percent one number is of another, and increasing by a percent — on numbers you bring.

  5Percent drillPrint 20

The electrical side of the arithmetic — Ohm's law at three levels, and series and parallel — lives with its drills at Ohm's law practice and series / parallel practice, each with its own worked examples.

Ver también

• Las fracciones en una cinta
• Leer una cinta rápido
• Triángulos rectángulos en la obra
• Métrico ↔ imperial
• Los porcentajes en el oficio
• Ejercicios