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Appetizers and Lessons for Mathematics and Reason
  online logic chapters  - the best starting point for further site exploration.  Bon Appetite.

7 Changing Units
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Why Slopes
and
More Math
Volume 3

Vol 2, Three Skills for Algebra covers many  topics in algebra and logic that students starting calculus should have mastered or will have to master. Also includes arithmetic review problems to catch common mistakes.  A fourth skill  gives a unifying theme for high school maths.

Content Guide
Foreword
Chapter Descriptions
1. Introduction
Calculus Appetizer (1983)
2. Second Preview Begins
2 Skier in Motion (V)
2 The Skier (V)
2. Position Dependent (V)
3 Slope & Extrema (V)
4 Single Factor Analysis (V)
4 Two Factor (V)
4 More Factors (V)
4 With Divisors (V)
5 Maxima & Minima Tests
6 Jumps & Discontinuities
8 Review  (optional)
9 On Calculus Studies
11 Slope of Slope
13  Acceleration
14 Limits & Error Control (V)
14 Limit of a Fn.
14. Limited Error Control
14 Signif. Digits
14 Cauchy Limits
14 Sequence Limits
14 Decimal Arith.
15 What is Slope (V)
15 Slope Calculation (V)
15 Slope, a Limit
15 Tangent Lines
15 Linear Approx.,
15 Limits via Algebra (V)
15 Recap.
PS.Chain Rule for Polys
PS Chain Rule- General  (V) -
PS More Chain Rule (V)
PS - Sign Analysis (V)
16 What is Velocity
17  What is Area
18 Integration
18 Area Calculation
18  Fn DefN, 6 Ways
19 Logs & Powers
19 Natural Log.
19 Exponential Fn.
20 What's Next
21 Add Vectors
22 Complex #'s
23 Complex #'s
23 Trig Identity
23 Proofs of.
24 Complex Logs etc

Units in Calculations:
7 Velocity
7 Varying Velocity Example
7. Velocity Calculation
7 Changing Units
7 Same Velocity  Motions
10 Slopes without Units.
10 Units & Slopes
10  Units in Cost vs. Quantity
10  How Units  Appear
10 Unit  Elimination
10 Partial Elimination
10 Interest & Units
12 More on Units

Appendices:

Pigeon Hole Principle
Constant Difference Thm
Continuous Functions
Rational Functions
Mean Value Theorem
One Side Range Theorem
Range On One Side Theorem
Integration & Lipschitz
 Continuity


These appendices continue the
decimal viewpoint of limits, error
control and continuity begun
in Chapter 14. The One Sided
 Range Theorem
is a postscript,
not in printed version.

Changing Units (Digression)

The measure or unit of slope, speed and velocity in the last example is given by the ratio [ km/min] or km per minute, or km per one sixtieth of an hour. But other units (or ratio of units) are possible. The question becomes: what units do you like for the expression of these quantities. It is possible to change units of time and distance.

Multiplying by the number 1 does not affect the value of an expression, but the number 1 can be written in many ways. Some, not all, are helpful. These different ways can sometimes help in changing the units used for the expression of a quantity. A few slope or velocity based examples follow. Note that [60min/1hr] = 1 implies the following
m1
=
- 4
3
km
min
= - 4
3
km
min
×1
=
- 4
3
km
min
× 60min
hr
=
- 4
3
· 60
1
km
min
min
hr
=
4
1
· 20
1
km
hr
=
-80 km
hr
   
m2
=
8
3
km
min
× 60min
hr
=
160 km
hr
m3
=
0
m4
=
- 1
2
km
min
× 60min
hr
= -30 km
hr
m5
=
- 3
2
km
min
× 60min
hr
= -90 km
hr
In summary, multiplying by 1 = [60min/hr] does not change the speed or velocity m, but it does help to change the units from minutes to hours. Note to do the reverse change, multiply by
1 = hr
60min
instead. Note that care must be taken in selecting the ratio of units whose value is 1. A faulty choice will introduce more units instead of permitting some to cancel.

Remark.   An alternate method is to substitute 1 min = [1/60] hr into an expression. For example
m2
=
8
3
km
min
=
8
3
 
km
1
60
hr
=
8
3
· 60
1
· km
hr
= 160 km
hr
as before. Substitution replaces one unit by an expression for it in terms of another. With this method, there is little or no hazard of introducing units that don't cancel, but the algebra or arithmetic requires a little more thought. The choice of unit conversion method depends on where you would like to do the work or reasoning.

 

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Math How-TOs
1. Arithmetic   2. Algebra   3.  More Algebra  4.  Geometry 5 More Geometry 6.  Calculus
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Online Volumes (orders)
1,  Elements of Reason. 1996
1A. Pattern Based Reason  1995
1B. Math Curriculum Notes 1996
2. Three Skills for Algebra  1995
3 .Why.Slopes.&
.More.Math.1995

Skill & Concept 
Review or  Development 

 1. Decimal Arith - Video Based ]
2   Fractions  
3.  Fractions  with Units  
3. Solving Linear Equations  - 
making alg easier
4. Formulas forwards & Backwards - unifying theme for Algebra
5.  Proportionality, Back- & For-wards - theme at work.
6.  Logic - Math Free, good for precision in  work & studies 
7. Euclidean-Geometry  (leanly)
8. Slopes and Lines 
9. Why Study Slopes - a context 
10.  Quadratics
11  Polynomials
12  Factored Polys - a context
13 Functions - For-& Back -wards
14  Number Theory, Richly
15. Exponents, Radicals & logs.  
16   Calculus - Examples & Advice 
17.   Real  Analysis 
18  Electric Circuits Etc (So So)
19 Maps, Similarity & Trig, (alt view)
20 Complex numbers  

21 Logic with Symbols+truth tables

22  Consistent Story Telling
23. Even More Logic

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