LA 2100 · Quadrivium: The School of Arithmetic — Module 5: Decimal Fractions and Money

Led by James B. Thomson Simulacrum

Where place value and fractions turn out to be one thing. The decimal point derived from symmetry rather than decreed, and money as the decimal currency it is.

1. Module 5

   Decimal Fractions and Money

   Led by James B. Thomson Simulacrum

   The question

   Eight sittings, Thomson's pages 129 to 157. You begin without

   Outcome

   The student can read, write and operate on decimal fractions of any

   Sub-units

   1. ○ 5.1 The Symmetry Argument Open this unit → ✓ ↻
   2. ○ 5.2 Notation: Reading and Writing Decimals Open this unit → ✓ ↻
   3. ○ 5.3 Reduction Between Decimals and Common Fractions Open this unit → ✓ ↻
   4. ○ 5.4 Addition and Subtraction of Decimals Open this unit → ✓ ↻
   5. ○ 5.5 Multiplication and Division of Decimals Open this unit → ✓ ↻
   6. ○ 5.6 Money as Decimal Currency Open this unit → ✓ ↻
   7. ○ 5.7 The Operations Applied to Money Open this unit → ✓ ↻
   8. ○ 5.8 Review and Selection Open this unit → ✓ ↻
   Begin the course → Print certificate of completion

   Practice scenarios

   The Misplaced Point

   You are checking accounts prepared by a competent clerk. The arithmetic is sound throughout — every addition, every extension correct — and the total is out by a factor of ten. He has checked it twice by re-adding and found nothing, because there is nothing wrong with the addition. He is beginning to doubt himself and is talking about checking every figure a third time.

   Your goals

   • Explain why re-adding cannot find this error, and what class of error it is
   • Locate the fault by order of magnitude rather than by recomputation
   • Say which of the module's principles the error violates
   • Give him a check that would catch it in seconds in future
   • Decide whether the fault is his, the source document's, or the form's

   Practise this scenario →